Reiny

Most popular questions and responses by Reiny
  1. @Peter, earlier question

    Peter, I found your question interesting and have been messing with it for a while www.jiskha.com/questions/1789041/Ethel-went-to-the-farmers-market-to-buy-some-eggs-not-in-a-dozen-cartons-on-the I finally made up a short computer program using a silly old

    asked on March 19, 2019
  2. algrbra

    Complimentary angles add up to 90º So translate the English into Math. if you let the unknown angle be x then "the measure of the compliment of the angle" -----> 90-x "10 degrees less than three times the measure of the angle" ----> 3x - 10 so....... 90-x

    asked on March 28, 2007
  3. To All Students & Tutors

    I will not be able to answer any questions on this board for the next 8 days or so. I will be warming my weary bones down south off one of the islands of Belize for a while. Great time to get away as the temperature up my way is currently at -12 C. Reiny

    asked on January 6, 2010
  4. @ Steve or Damon

    take a look at this question http://www.jiskha.com/display.cgi?id=1446147947 Am I guilty of overkill or over-thinking this ? Surely there has to be an easier way.

    asked on October 29, 2015
  5. To Jessica

    I have now corrected two of your replies in which you gave incorrect solutions. Unless you know what you are doing, please don't answer any questions dealing with topics not familiar to you . I know everybody makes mistakes, I make my share, but those are

    asked on January 31, 2013
  6. For <b>marie flore joseph</b>

    Please do not add your new question as a response to somebody else's post. click on "Post a New Question" above to post your problem. Here is your question : Math - marie flore joseph, Monday, April 5, 2010 at 10:37pm the difference of the squares of two

    asked on April 5, 2010
  7. principles of finances

    according to my interpretation of the question in October they would collect: the 10% of the August sales = .10($10,000) the 20% of the Sept sales = .20($20,000) and the 70% of the Oct sales = .70($30,000) Do the arithmetic and add them up A project has an

    asked on March 28, 2007
  8. For Anubhav

    re http://www.jiskha.com/display.cgi?id=1368707176 I have a solution, but what a mess. Before I type it all out, let me know if you still need the solution. I certainly don't feel like typing it all out unless you will actually look at it.

    asked on May 16, 2013
  9. Vectors

    I hope that the diagram I have drawn for myself matches the one in your question. I have a triangle with sides 20 and 10 and an angle of 120º between them By the cosine law I found the third side to be 26.4575. You said you found the maginitude, I hope we

    asked on April 20, 2007
  10. For Lily

    Please do not append a new question at the end of somebody else posting. Your question will likely be passed over, since most tutors will not look at a posting if they see that it has been answered. http://www.jiskha.com/display.cgi?id=1278474837

    asked on July 7, 2010
  11. For Hannah

    Re http://www.jiskha.com/display.cgi?id=1369225544 Sorry to have caused confusion for you Hannah. In your original post, you had 3 different problems, the first two were "volume" questions. When I did the third one, which was simply finding an area, I

    asked on May 22, 2013
  12. Message to Students re Math

    Just thought I would let you young'nes know that being a Mathematician has just been chosen as the most rewarding profession. http://online.wsj.com/article/SB123119236117055127.html?mod=yhoofron Now I know why I have been so happy all my life, lol So keep

    asked on January 8, 2009
  13. math

    You did not watch your units, you are mixing inches and feet Your equation should have been 1/2 = 1/di + 1/120 (I changed 10 feet to 120 in) solve this for di and you get 2.03 inches. Please help me I am so confused I think I am losing my mind. The focal

    asked on May 9, 2007
  14. Nice unanswered question by Maggie

    "100 bushels of corn are divided among 100 men, women, and children. Men receive 3 bushels each, women 2 bushels and children 1/2 bushel each. How can the bushels be distributed? is there more than one solution? if so, find the other solutions." let the

    asked on September 16, 2009
  15. algebra

    I trust you know about y = mx + b Realize that when you are given the x or y intercepts, you are really just given two points, in your case the points (4,0) and (0,-2) So it is easy to find the slope, (-2-0)/(0-4) = 1/2 Take it from there Determine the

    asked on March 28, 2007
  16. for Knights

    have been looking at your post ... http://www.jiskha.com/display.cgi?id=1357047578 interesting question... let the altitude of 12 hit base a let the altitude of 14 hit base b then (1/2)(12)a = (1/2)(14)b 6a = 7b a = 7b/6 let the third side be c and its

    asked on January 1, 2013
  17. MathMate - look at this

    perhaps you can shed some light on this I seem to have a "mental block" here. http://www.jiskha.com/display.cgi?id=1292296754

    asked on December 13, 2010
  18. FOR NABIAH

    You now have 6 different posts going for the same "cake question" I am not going to keep going back to see which one you replied to. Stay with one posting please. I just notice one way down the list where you did part a) Calculate the area on top of the

    asked on April 22, 2010
  19. Monitors of Board

    Is there any way that the postings could be numbered? The post below this one by TONY obviously refers to a previous posting of his 8 steps below. I know the URL has a number behind each particular post, and each post can be identified by a title and

    asked on March 20, 2007
  20. For Lia - question from this morning

    I took some time to work out your rather "nasty" Calculus question. Take a look at it and see if it matches your expected result. http://www.jiskha.com/display.cgi?id=1300878253

    asked on March 23, 2011
  21. Happy Pi Day

    Happy Pi Day to all math "nerds" Even Google changed their log today. http://www.squidoo.com/PiDay

    asked on March 14, 2010
  22. Message for KMTRENd

    One would have thought that the least you could have done was give an acknowledgment for a most extraordinary reply you got to your question by tchrwill http://www.jiskha.com/display.cgi?id=1265187860

    asked on February 3, 2010
  23. For MUFFY

    You stated on Saturday that you understood my solution as far as part a) and b) were, so let me just recap what we did. (I will not repeat the actual question) My Solution: Suppose we label the point of contact P(x,y). I bet P is in the first quadrant. but

    asked on October 5, 2009
  24. For George

    At 11:37 and at 12:24 you posted the same question the earlier one was answered correctly by drwls by accepting your question the way you typed it. my solution is based on the assumption that your denominator was e^(t-7), an invalid assumption.

    asked on September 11, 2008
  25. math

    break it down into cases at most one day of rain in 3 days to me means we could have: norain norain norain ----> (1/3)^3 = 1/27 rain norain norain -------> 2/3(1/3^2 = 2/27 norain rain norain -------> same as above = 2/27 norain norain rain -------> same

    asked on May 17, 2007
  26. help, bobpursely

    Please take a look at DEVON's trig equation at 9:14 I must be missing something obvious. If the second had been 3sin 2x it would be a straight forward question. The way it stands I was able to "reduce" it to the equation 8sin^4 x - 8sin^2 x + 3sin x + 2 =

    asked on April 16, 2007
  27. calc

    I assume the poster was trying to type "oblique asymptote" from your answer of 3x+2 + 7/(x-1) we can conclude that there is an oblique linear asymptote of y = 3x + 2, and a vertical asymptote at x = 1 for the original function given. how do u find obblique

    asked on March 26, 2007
  28. factoring

    let f(m)=m^3 + 3m^2 + 3m + 1 notice f(-1) = 0, so m+1 is a factor. Using division, the answer is m^2 + 2m + 1 which factors once more to (m+1)(m+1) so you have (m+1)^3 = 0 and then m = -1 Are you familiar with Pascal's triangle? Did you notice the pattern

    asked on March 11, 2007
  29. Attention: Courtney's Dad

    http://www.jiskha.com/display.cgi?id=1224954147

    asked on October 26, 2008
  30. Reiny to Gina (logic)

    I saw your reply re my late night solution to your pumpkin question http://www.jiskha.com/display.cgi?id=1224212047 I did indeed make two typing errors, which even though they do not change the actual answer, nevertheless would have caused confusion. I

    asked on October 17, 2008
  31. Algebra

    3(2+3-2(4-5)2-1)-3(2+4(4-2)-8+3(2-5)+1-2)1-3)+4-5 rather silly question, and some of it makes no sense eg look at the first part ......-2(4-5)2-1 does this end up -2(-1)(2) ? or did you forget an operator before the last 2? there is a similar discrepancy

    asked on August 21, 2007
  32. maths

    Set it up this way: Let the number of students be x let the number of rows be y then the number of students per row is x/y This results in 2 equations from your data: (x/y+1)(y-2) = x and (x/y-1)(y+3 = x Solve these two, gets a bit messy at first but it

    asked on July 15, 2007
  33. I can write it instead

    Leo, a similar prediction is often made about arithmetic since the invention of the calculator. in one of Isaac Asimov writings they discover a man who is actually able to perform an operation like 368 x 4821 with something called a pencil and paper. My

    asked on May 15, 2007
  34. Trig

    I don't know the physics behind Snell's Law, but I can do the math Snell's Law says sin(angle of incidence)/sin(angle of reflection) = refractive index since you know the two angles... sin45/sin27 = refractive index =1.5575365 so for an angle of refection

    asked on April 19, 2007
  35. math

    There is no function equation for the Fibonacci numbers, you have to use a Recursion formula. F(n) = F(n-1) + F(n-2) for n>2 and F(1)=1, F(2)=1 what is the equation for the fibonacci sequence

    asked on March 11, 2007
  36. For Haley

    Even though you mean well, your last three responses have been either incomplete or incorrect. The one to http://www.jiskha.com/display.cgi?id=1258225501 is totally off the mark. Please make sure you are familiar with the topic before replying.

    asked on November 14, 2009
  37. college Algebra

    This is "college" math? Anyway... let the smaller number be x, and the larger number be x+8 then x + x+8 < 12 this is easy to solve, let me know what you got. the sum of two numbers is less than 12. The second number is 8 more than the first.what are the

    asked on July 25, 2007
  38. algebra

    These are very easy to set up with a "chart" ---------Distance-----Rate---Time (D=RxT) slow way --6x----------x-------6 fast way - 5(x+7)-----x+7------5 so 6x = 5(x+7) 6x=5x+35+ x=35 The speed on the slower trip was 35 mph, and on the return trip 42 mph A

    asked on June 17, 2007
  39. Vectors-another angle confusion

    On an x-y grid, label them N-S, E-W, draw a line from the origin to the right and label it 425 (you are going East) From the end of that line draw a vertical line upwards of 40 (you are going North) Use an approximate scale, realizing that 425 is just

    asked on April 20, 2007
  40. To Math Students, re √ sign

    Several student tonight have asked me how I create the √ symbol to create √ symbol on a PC, hold down the Alt key, and at the same time press 251 on the number pad, then release the Alt key on Mac, hold down the Option key, and press V, release the

    asked on June 9, 2010
  41. math.algebra

    other than factoring out the 9 there is really no simplification that can be made here 9sqrt6 - 9sqrt2 =9(√6 - √2) can someone help me simplify: 9sqrt6 - 9sqrt2

    asked on July 29, 2007
  42. math

    how about (5-3)x2 + 8(5-2) ? To me these are really just "puzzles" and do not actually require much mathematical ability. The best and often only way is to by 'trial and error'. what is the rule when grouping numbers? example I want the answer to be 28. 5

    asked on March 28, 2007
  1. math

    Length ---- y each of the 4 width --- x so 2y + 4x = 1200 y = 600 - 2x area of whole pen = xy = x(600-2x) = 600x - 2x^2 d(area...)/dx = 600 - 4x = 0 for a max of area 4x = 600 x = 150 take over

    posted on October 19, 2019
  2. Math

    Not enough information, we can't see any line

    posted on October 19, 2019
  3. algebra

    Mmmh, since 4178 is even, it clearly cannot be prime. The largest prime I had to consider was 2 as a divisor, and since 4178 is divisible by 2, it is not a prime

    posted on October 19, 2019
  4. math

    You are not accounting for people subscribing to all 3 which would be included in the double intersection values of 38, 20, and 28 n(N or W or U) = n(W) + n(N) + n(U) - n(W and N) - n(W and U) - n(N and U) + n(W and N and U) 300 = 150+122+62 - 38 - 28 - 20

    posted on October 18, 2019
  5. MATHS

    A: boys : girls = 4x : x B: boys : girls = 2y : 3y 4x+x = 2(2y+3y) 5x = 10y x = 2y boysA : boysB = 4x :2y = 8y:2y = 4:1 b) 2y-10 : 3y-10 = 1 : 2 (2y-10)/(3y-10) = 1/2 4y - 20 = 3y - 10 y = 10 then since x = 2y, x = 20 and total is A is 5x = 100

    posted on October 18, 2019
  6. math

    same source as mine No page seems to have a valid algebraic solution.

    posted on October 18, 2019
  7. math

    Have seen this in an old math book. You start with 3 people. At the end of first day, the 3 people now have 3 days' food each, one person give a days' food to the other two, so 2 people now have 4 days' food and the 1st has a days' food left and heads

    posted on October 18, 2019
  8. maths

    Let the distance between home and school be 2x So they met after x metres. Sister went for t minutes at 50 m/min , so x = 50t Eddie went for (t-5) minutes at 60 m/min so x = 60(t-5) but those are equal, so 60(t-5) = 50t 60t - 300 = 50t t = 30 then x =

    posted on October 18, 2019
  9. math

    "that slows its speed to of its average speed up to the time of the failure" something missing here.

    posted on October 18, 2019
  10. math

    After doing your 3:00 pm post, I realized that you are working with the ambiguous case so angle B could be either 26.4° or 153.6° so the triangle could be either acute OR obtuse, choice #4

    posted on October 18, 2019
  11. math

    nope by the sine law sinB/8 = sin30/5 sinB = 4/5 B = 53.1° or 180-53.1° = 126.9° by the CAST rule

    posted on October 18, 2019
  12. math

    Agree, I got angle C >90° btw, choice 4 is rather silly, because it is also a correct choice.

    posted on October 18, 2019
  13. Math

    Your original question is incomplete. However, for x^2-2xy+y^2+4x-8y+20=0 2x - 2x(dy/dx) - 2y + 2y(dy/dx) + 4 - 8dy/dx = 0 dy/dx(-2x + 2y - 8) = -2x + 2y - 4 dy/dx = (-2x + 2y - 8)/(-2x + 2y - 4) = (x - y + 4)/(x - y + 2) btw, this is what your graph looks

    posted on October 18, 2019
  14. Math

    1/4 divided by 3/8 To divide one fraction by another, instead multiply the first fraction by the reciprocal of the second 1/4 ÷ 3/8 = (1/4)(8/3) = 8/12 = 2/3 Do the others in the same way

    posted on October 18, 2019
  15. Maths

    or 14 men can cultivate 42 acres of land in 18 weeks 1 man can cultivate 42/14 or 3 acres of land in 18 weeks 1 man can cultivate 1 acre of land in 6 weeks 21 men can cultivate 1 acre of land in 6/21 or 2/7 weeks 21 men can cultivate 56 acres of land in

    posted on October 18, 2019
  16. Math

    what is 22.5 ÷ .75 ??

    posted on October 18, 2019
  17. Arithmetic progression

    a = 3 term(8) = a + 7d 3 + 7d = 31 solve for d

    posted on October 18, 2019
  18. Algebra

    Of course.

    posted on October 18, 2019
  19. Algebra

    For any y = mx + b m, the number in front of the x term, is the slope, or the rate of change. The greater the value of m, the greater the rate of change. Do you want to change your answer?

    posted on October 18, 2019
  20. maths

    I am assuming that you are depositing $60 right now, and that there are 9 terms in the series Amount = 60(1.07)^8 + 75(1.07)^7 + 90(1.07)^6 + .... + 150(1.07)^2 + 165(1.07) + 180 It would take you only about 5 minutes on a good calculator with memory

    posted on October 18, 2019
  21. Math repost

    No Look at this excellent video by Mr. Khan from Khan's Academy then follow the steps https://www.khanacademy.org/math/cc-sixth-grade-math/cc-6th-data-statistics/cc-6-mad/v/mean-absolute-deviation

    posted on October 17, 2019
  22. Maths

    N2! ?? , so that would be like 2N ?? let N2! = x 3(x+24) = 2x 3x + 72 = 2x x = -72 N2! = -72 N = -36

    posted on October 17, 2019
  23. Algebra

    9 - c < 2 OR -3c > 15 -c < -7 OR -c > 5 c > 7 OR c < -5 On a number line, draw a line to the left with an arrow at its end starting at -5 and a line with an arrow at its end to the right of 7

    posted on October 17, 2019
  24. math

    just use the traditional way to add fractions ... -1/6 + (-3/7) = -7/42 - 18/42 = -25/42

    posted on October 17, 2019
  25. Math

    Looks like the application of the standard compound interest formula amount = principal(1 + i)^t The $500 is the principal or "starting amount" D is correct

    posted on October 17, 2019
  26. math

    Let the selling price be k, where k is a constant let the number of box originally sold be c, where c is a constant let the number of price increases by n number sold = c - 2n selling price = k + 25n profit = (c-2n)(k + 25n) = ck + 25cn - 2kn - 50n^2

    posted on October 17, 2019
  27. Calculus

    I assume you are solving. You will have to use some kind of iterative method such as Newton's Method let y = sec^2(x) - 2x dy/dx = 2(secx)(secx tanx) - 2 = 2 sec^2 x tanx - 2 Newton: newx = x - (sec^2 x - 2x)/(2 sec^2 x tanx - 2) pick any x find newx if

    posted on October 17, 2019
  28. Math

    So you are looking for a number which 1. when divided by 4 leaves a remainder of 3 2. when divided by 5 leaves a remainder of 3 3. when divided by 6 leaves a remainder of 1 Since we are dealing with relatively small numbers we can just list the sequences

    posted on October 16, 2019
  29. math

    #1 number( CUH) = number(C) + numbr(H) - number (C∩H) = 20 + 15 - 5 = 30 You had 20+ 15 -15-5 =30 , probably a typo in the -15 It asked for the prob P(CUH) = 30/60 = 1/2 #2, Venn diagram are quite easy, especially when the data is nicely presented. Draw

    posted on October 16, 2019
  30. math

    Volume of sphere = (4/3)π r^3 You said the result is a 3 digit integer time π So r^3 must be an integer if r is to be an integer perfect cubes are 1,8,27, 64, 125, 216, 343, 512, 729, 1000 4/3 times those must remain a 3 digit integer. which means the 3

    posted on October 16, 2019
  31. Math

    base10: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 .... base6: 1 2 3 4 5 10 11 12 13 14 15 20 21 22 23 24 25 30 ... hard to line them up so they match.

    posted on October 16, 2019
  32. Math

    Prob(at least 2 girls) = 1 - prob(no girls) - prob(exactly 1 girl) = 1 - C(9,0) (1/2)^0 (1/2)^9 - C(9,1) (1/2) (1/2)^8 = 1 - (1/2)^9 - 9(1/2)^9 = 1 - 1/512 - 9/512 = 251/512 or appr .98 prob(at most 3 girls) prob(exactly 1 girl) + prob(exactly 2 girls) +

    posted on October 16, 2019
  33. math

    It said "simplified" 72/100 is not simplified,

    posted on October 16, 2019
  34. math

    What part of oobleck's solution did you not like for this problem? https://www.jiskha.com/questions/1805169/A-new-car-is-sold-for-its-sticker-value-of-19-400-Three-years-later-the-customer The strange part is that you even thanked him for it. As to your

    posted on October 16, 2019
  35. math

    or let the bundles contain 3x and 5x papers 3x+5x=64 8x=64 x = 8 so 3x ---> 24 and 5x ---> 40

    posted on October 15, 2019
  36. Math

    There were 5 responses in that link, including your own. If it was not you, then choose an identifiable name instead of Anonymous.

    posted on October 15, 2019
  37. Math

    same question here: looks like it was your own https://www.jiskha.com/questions/1805131/Matthew-earns-400-per-week-plus-a-3-commission-on-everything-he-sells-Write-and

    posted on October 15, 2019
  38. Math

    Two steps: 1. add 1 to both sides 2. multiply both sides by 5 done

    posted on October 15, 2019
  39. math

    27° - (-12°) = 39° change in 9 hours Became curious what the greatest change per day in history was, so .... The largest recorded temperature change in one place over a 24-hour period occurred in Jan 1972 in Loma, Montana, when the temperature rose from

    posted on October 15, 2019
  40. Math

    The area of two circles is proportional to the square of the radii. .9area/1area = r1^2 / r2^2 (r1/r2)^2 = .9 r1/r2 = √.9 = appr .949 so it is reduced by 5.1% another way: take a specific case suppose the radius is 12 cm then the area is 144π cm^2 If we

    posted on October 15, 2019
  41. math

    prob( less than 2 cars) = prob(sell none) + prob(sell 1) =

    posted on October 15, 2019
  42. Math

    prob(good) = .91 prob(not good) = .09 prob(at least defective) = 1 - prob(all good) = 1 - .91^10 = .....

    posted on October 15, 2019
  43. algebra

    -3 < -x -2 < 4 add 2 to each part -1 < -x < 6 divide each part by -1, remember when dividing or multiplying by a negative the inequality sign has to be reversed. 1 > x > -6 or, turning it around -6 < x < 1

    posted on October 15, 2019
  44. Math

    I just took the sentence "They both traveled the same distance" and translated it into math Look at my steps, one distance was 9t and the other was 3(t+4) but they are EQUAL, so 9t equals 3(t+4) 9t = 3(t+4)

    posted on October 15, 2019
  45. Math

    Beneta's time ---- t hours Sarah's time ---- t+4 hours distance gone by Beneta = 9t , using distance = rate x time distance gone by Sahra = 3(t+4) but they went the same distance, thus ... 9t = 3(t+4) solve for t and you got it.

    posted on October 15, 2019
  46. Math

    600000 = 200000 + 300000+ 100000 commission = .04(200000) + .06(300000) + .08(100000) = ... number sold = 600000/2000 = ...

    posted on October 15, 2019
  47. geometry

    Did you mean: " ... such that AB is 2/3 of AC" ?

    posted on October 14, 2019
  48. Math

    Yes, Pythagoras would be your proof.

    posted on October 14, 2019
  49. Maths

    Poor wording. The sum of 11 what? 11 terms? I will assume that You must know your 2 main formulas for an AP term(n terms) and sum(n terms) sum(11) = 11/2(2a + 10d), but you told me that sum(11) = 891 and d = 15 so let's sub that into the above 891 =

    posted on October 14, 2019
  50. math

    Why not just say: y+7 = (-2/5)(x-10) , instead of that gibberish ?? steps: multiply each side by 5 further expand the right side make sure all terms x and y are on the left side, and the constant is on the right side. Pick the matching answer, all done

    posted on October 14, 2019
  51. Algebra

    The perimeter of the original square is 16 ft so each side is 4 ft How did I get 4 ft as the length of a side ?? now the new square will be 28 ft on each side, so .....

    posted on October 14, 2019
  52. algebra

    type it this way: √(12x^20 y^8) = √12 √(x^20) √(y^8) = 2√3 x^10 y^4

    posted on October 14, 2019
  53. Calculus

    Nice assignment, but how do you expect us to do this when it clearly involves using a graphing app ? I will do #2, since it is a classic question that simply follows the definition of an ellipse. (A good teacher will actually demonstrate this for the class

    posted on October 14, 2019
  54. Math

    If C is your choice, then each cookie costs $1 and the 3 cookies would cost $3.00 But it said they cost $2.97, mmmmh, that would be out 3 cents Let's see 3 cents off for 3 cookies, ...... ????? Quit guessing.

    posted on October 14, 2019
  55. algebra

    Nothing can be done to 12x^20 y^8 in terms of simplifying it. Did you type it correctly? What were the instructions for the question?

    posted on October 14, 2019
  56. math

    You must be studying the binomial expansion I hope your teacher has made you aware of Pascal's Triangle. Look at the row that starts with 1,5 ... It should be 1 5 10 10 5 1 and (p+3)^5 = p^5 + 5(p^4)(3) + 10(p^3)(3^2) + 10(p^2)(3^3) + 5(p)(3^4) + 3^5 = p^5

    posted on October 14, 2019
  57. Math

    1.45*cost = 129.99 cost = 129.99/1.45 = ...

    posted on October 14, 2019
  58. Math

    Probably contains a typo, was -24 supposed to be -24x ? Poorly worded, did you mean: Determine the equation of the inverse of f(x) = 2x^2 + 24x - 3 ? If so, the inverse of f(x) is not a function. Waiting for a cleanup.

    posted on October 13, 2019