Reiny
Most popular questions and responses by Reiny
@Peter, earlier question
Peter, I found your question interesting and have been messing with it for a while www.jiskha.com/questions/1789041/Ethelwenttothefarmersmarkettobuysomeeggsnotinadozencartonsonthe I finally made up a short computer program using a silly old
asked on March 19, 2019 
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" > 90x "10 degrees less than three times the measure of the angle" > 3x  10 so....... 90x
asked on March 28, 2007 
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 
@ Steve or Damon
take a look at this question http://www.jiskha.com/display.cgi?id=1446147947 Am I guilty of overkill or overthinking this ? Surely there has to be an easier way.
asked on October 29, 2015 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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, (20)/(04) = 1/2 Take it from there Determine the
asked on March 28, 2007 
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 
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 
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 
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 
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 
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 
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 
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 
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^(t7), an invalid assumption.
asked on September 11, 2008 
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 
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 
calc
I assume the poster was trying to type "oblique asymptote" from your answer of 3x+2 + 7/(x1) 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 
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 
Attention: Courtney's Dad
http://www.jiskha.com/display.cgi?id=1224954147
asked on October 26, 2008 
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 
Algebra
3(2+32(45)21)3(2+4(42)8+3(25)+12)13)+45 rather silly question, and some of it makes no sense eg look at the first part ......2(45)21 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 
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)(y2) = x and (x/y1)(y+3 = x Solve these two, gets a bit messy at first but it
asked on July 15, 2007 
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 
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 
math
There is no function equation for the Fibonacci numbers, you have to use a Recursion formula. F(n) = F(n1) + F(n2) for n>2 and F(1)=1, F(2)=1 what is the equation for the fibonacci sequence
asked on March 11, 2007 
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 
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 
algebra
These are very easy to set up with a "chart" DistanceRateTime (D=RxT) slow way 6xx6 fast way  5(x+7)x+75 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 
Vectorsanother angle confusion
On an xy grid, label them NS, EW, 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 
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 
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 
math
how about (53)x2 + 8(52) ? 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

math
Length  y each of the 4 width  x so 2y + 4x = 1200 y = 600  2x area of whole pen = xy = x(6002x) = 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 
Math
Not enough information, we can't see any line
posted on October 19, 2019 
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 
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 
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) 2y10 : 3y10 = 1 : 2 (2y10)/(3y10) = 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 
math
same source as mine No page seems to have a valid algebraic solution.
posted on October 18, 2019 
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 
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 (t5) minutes at 60 m/min so x = 60(t5) but those are equal, so 60(t5) = 50t 60t  300 = 50t t = 30 then x =
posted on October 18, 2019 
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 
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 
math
nope by the sine law sinB/8 = sin30/5 sinB = 4/5 B = 53.1° or 18053.1° = 126.9° by the CAST rule
posted on October 18, 2019 
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 
Math
Your original question is incomplete. However, for x^22xy+y^2+4x8y+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 
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 
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 
Math
what is 22.5 ÷ .75 ??
posted on October 18, 2019 
Arithmetic progression
a = 3 term(8) = a + 7d 3 + 7d = 31 solve for d
posted on October 18, 2019 
Algebra
Of course.
posted on October 18, 2019 
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 
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 
Math repost
No Look at this excellent video by Mr. Khan from Khan's Academy then follow the steps https://www.khanacademy.org/math/ccsixthgrademath/cc6thdatastatistics/cc6mad/v/meanabsolutedeviation
posted on October 17, 2019 
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 
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 
math
just use the traditional way to add fractions ... 1/6 + (3/7) = 7/42  18/42 = 25/42
posted on October 17, 2019 
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 
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 = (c2n)(k + 25n) = ck + 25cn  2kn  50n^2
posted on October 17, 2019 
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 
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 
math
#1 number( CUH) = number(C) + numbr(H)  number (C∩H) = 20 + 15  5 = 30 You had 20+ 15 155 =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 
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 
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 
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 
math
It said "simplified" 72/100 is not simplified,
posted on October 16, 2019 
math
What part of oobleck's solution did you not like for this problem? https://www.jiskha.com/questions/1805169/Anewcarissoldforitsstickervalueof19400Threeyearslaterthecustomer The strange part is that you even thanked him for it. As to your
posted on October 16, 2019 
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 
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 
Math
same question here: looks like it was your own https://www.jiskha.com/questions/1805131/Matthewearns400perweekplusa3commissiononeverythinghesellsWriteand
posted on October 15, 2019 
Math
Two steps: 1. add 1 to both sides 2. multiply both sides by 5 done
posted on October 15, 2019 
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 24hour period occurred in Jan 1972 in Loma, Montana, when the temperature rose from
posted on October 15, 2019 
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 
math
prob( less than 2 cars) = prob(sell none) + prob(sell 1) =
posted on October 15, 2019 
Math
prob(good) = .91 prob(not good) = .09 prob(at least defective) = 1  prob(all good) = 1  .91^10 = .....
posted on October 15, 2019 
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 
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 
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 
Math
600000 = 200000 + 300000+ 100000 commission = .04(200000) + .06(300000) + .08(100000) = ... number sold = 600000/2000 = ...
posted on October 15, 2019 
geometry
Did you mean: " ... such that AB is 2/3 of AC" ?
posted on October 14, 2019 
Math
Yes, Pythagoras would be your proof.
posted on October 14, 2019 
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 
math
Why not just say: y+7 = (2/5)(x10) , 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 
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 
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 
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 
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 
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 
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 
Math
1.45*cost = 129.99 cost = 129.99/1.45 = ...
posted on October 14, 2019 
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