Reiny
Newest questions and responses by Reiny
@ 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 
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 
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 17, 2013 
Happy π Day to all mathematicians
Today, March 14, at 1:59 was a very special time.
asked on March 14, 2013 
Damon or Steve or bobpursley or drwls or ...
any ideas ? , looks way too messy for here http://www.jiskha.com/display.cgi?id=1361092708
asked on February 17, 2013 
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 February 1, 2013 
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 
For MathMate or bobpursley  check this
Can somebody take a look at this? http://www.jiskha.com/display.cgi?id=1318555635
asked on October 14, 2011 
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 
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 14, 2010 
For Carry, Alissa,Courtney, Max
Please do not switch names, it causes unnecessary and duplicate replies from tudors.
asked on November 14, 2010 
Happy Thanksgiving Canada
Happy Thanksgiving to my fellow Canadian tutors and to the Canadian students at Jiskha.
asked on October 11, 2010 
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 
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 10, 2010 
ATTENTION Ms Sue
spamming here http://www.jiskha.com/display.cgi?id=1274987816
asked on May 27, 2010 
Ms Sue  Welcome back
hope you had a great trip
asked on May 12, 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 
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 6, 2010 
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 
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 7, 2010 
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 
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 6, 2009 
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 
Attention : Caroline
check your post from http://www.jiskha.com/display.cgi?id=1239151481
asked on April 8, 2009 
All Done
Ok, logging off, night all.
asked on February 25, 2009 
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 
Attention : H Masri
re your post from late last night http://www.jiskha.com/display.cgi?id=1225941973
asked on November 6, 2008 
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 
Is Form Going to the dogs?
sorry, just couldn't resist that.
asked on October 7, 2008 
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 
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 22, 2007 
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 
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 26, 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 
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 
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 18, 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 
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 
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 
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 
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 
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 17, 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 
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 
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 
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 
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 
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 21, 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 12, 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 12, 2007

math
correct
posted on January 24, 2019 
Math
#1, correct #2 , you have no choices, nor do you give an answer but 4/5 of 40 = 32 #3, correct #4, since 1/6 is greater than 1/7, you used more ribbon than you had !!!! wow #5, you gave no answer, but what is 2/5 of 4 ???
posted on January 24, 2019 
Math
Did you mean: The quantity y is partly constant AND varies as the square x> I will assume you did. so y = a x^2 + c when x=1, y=11 > 11 = a + c when x=2, y=5 > 5 = 4a + c subtract those two equations: 6 = 3a a = 2, then c = 13 y = 2x^2 + 13 plug
posted on January 23, 2019 
Algebra
Area of garden itself = 20(15) ft^2 = 300 ft^2 Area of walk and garden = (20+2x)(15+2x) ft^2 area of walk alone = A(x) = (20+2x)(15+2x)  300 ft^2 Now plug in x = 3 and evaluate
posted on January 23, 2019 
Algebra
Your equation should say h(t) = 16t^2 + 528t  1440 , not cubed Besides that, it would have that function only after it leaves the water. It would be different in the water. So I will let you fix that
posted on January 23, 2019 
Calculus HELP ASAP
If I were you, I would use an example of each type and find its derivative. That would tell me the answer.
posted on January 23, 2019 
Math
https://www.jiskha.com/questions/1783791/Producingamusicalcosts8000plus300perperformanceOnesoldoutperformance
posted on January 23, 2019 
Math
number of performance  n expenses = 8000 + 300n revenues = 700n when are they equal?
posted on January 23, 2019 
math
2y=2y is an identity, since 0 = 0 it is true for all values of y
posted on January 23, 2019 
Calculus HELP ASAP PLS
suppose y = e^x y' = e^x y'' = e^x = y
posted on January 23, 2019 
Math
I told you it factored 5x^2  31x + 6 = 0 (x6)(5x1) = 0 x = 6 or x = 1/5 if x = 6, your terms are: 25, 10, and 4 notice 10/25 = 4/10 = 2/5 if x = 1/5, your terms are : 9/5, 21/5, and 49/5 is (21/5) ÷ (9/5) = (49/5) ÷ (21/5) ??
posted on January 23, 2019 
Math
number of choices of math books = C(4,2) = 6 number of choices of one of x others = C(x,1) = x 6x = 30 x = 5 So she got 4 math books and 5 others, or 9 in total
posted on January 23, 2019 
Math
Use your definition. (x+4)/(4x+1) = (10x)/(x+4) (x+4)^2 = (4x+1)(10x) x^2 + 8x + 16 = 40x  4x^2 + 10  x 5x^2  31x + 6 = 0 solve for x, it factors
posted on January 23, 2019 
math
Chris: 20 + 3n Kyle : 40 + n they are equal when 20+3n = 40+n solve for n
posted on January 22, 2019 
Math
did you make a sketch? Draw a common diameter. The radius of the larger circle will be b/2, and that of the smaller circle is a/2 draw the tangent so that it hits the end of the diameter. you will have a rightangled triangle, so that (b/2)^2 = (c/2)^2 +
posted on January 22, 2019 
Math
If you want the profit/loss on the total, add up the buying costs and the selling costs. Subtract the two and divide by the buying total There will be a loss
posted on January 22, 2019 
Math
looks like 4 gal : 36 miles = g gal : d miles 1/9 = g/d d = 9g for each of the unknown cases, just plug in e.g. when d = 9 , g = ? 9 = 9g g = 1
posted on January 22, 2019 
help
Area of a rectangle is length x width, so that is 8 x 4 or 32 square inches, the triangle is (1/2) x base x height so that is (1/2) x 4 x 3 = 6 square inches Add the two areas for your final answer.
posted on January 21, 2019 
help
They have actually given you more information than needed, but anyway... Draw a horizontal line at the top of the 8 inch line to meet the 11 inch line So now you have a rectangle 8 by 4 , and a rightangled triangle with sides 3,4, and 5. You should know
posted on January 21, 2019 
math
Obviously, digits must be allowed to repeat, otherwise the smallest combination would be 1234, and that sum is 10 So allowable choices: 1113 > arrange in 4!/3! or 4 ways 1122 > arrange in 4!/(2!2!) = 6 ways so there are 10 such numbers. So if you
posted on January 21, 2019 
Math
Don't know what you are asking, but did you notice that the numbers decrease by 4 ?
posted on January 21, 2019 
math
f(x)=4x(1/x) or y = 4x  1/x step 1 of inverse: interchange the x and y's x = 4y  1/y multiply by y xy = 4y^2  1 y = 1/2 xy' + y = 8y y' xy'  8y y' = y y'(x8y) = y y' = y/(x8y) = y/(8y  x)
posted on January 21, 2019 
math
y=x+sin(xy) You will need the product rule for the sine term dy/dx = 1 + cos(xy)(xdy/dx + y) the second dy/dx is imbedded in a product so we have to expand I will use y' for dy/dx y' = 1 + xcos(xy)*y' + ycos(xy) y'  xcos(xy) y' = 1 + ycos(xy) y' (1 
posted on January 21, 2019 
math
y^2 = 1 + 2/x 2y dy/dx = 2/x^2 y' = 2/(2yx^2) = 1/(y x^2) using the quotient rule, y '' = (yx^2(0)  (1)(x(2x) + x^2 dy/dx) )/(y^2 x^4) = (2xy + x^2(1/(yx^2) )/(y^2x^4) = (2xy  1/y)/(y^2 x^4) = (2x y^2  1)/(y^3 x^4) check my algebra
posted on January 21, 2019 
math
rephrasing your function: Let f(x)= sin(pi(x)) , 0 ≤ x ≤ 1 a(x)+b , 1 ≤ x ≤ 2 f ' (x) = πcos(πx) f ' (1) = 1 since x = 1 lies in the domain of the first part of the f(x), and πcos(π) = 1, the values of a and b don't enter the picture.
posted on January 21, 2019 
math
dy/dx = 2sin(2x) when x = π/6 slope = dy/dx = 2sin (π/3) = 2(√3/2) = √3 when x = π/6, y = cos(π/3) = 1/2 so you have the point (π/6 , 1/2) and the slope of √3 Find the equation of the tangent using your favourite method.
posted on January 21, 2019 
Math
Using the quadratic formula: x = (1 ± √(1  4(5)(k) )/1 = (1 + √(1+20k))/10 or x = (1  √(1+20k))/10 then (1 + √(1+20k))/10  (1  √(1+20k))/10 = 1.8 (1 + √(1+20k))  (1  √(1+20k)) = 18 2√(1+20k) = 18 √(1+20k) = 9 square both sides,
posted on January 20, 2019 
MATH
Are you just throwing out guesses? How many hours from noon to 9:00 pm ?? starting at +6 it decreases 4° each hour, so .....
posted on January 20, 2019 
Math
You did not answer Ms Pi when she asked which digits repeat She took it that all the digits repeat, and got the correct answer of 476/999 and the difference in the digits was not 259 So, again, which digits repeat ? .476476476... , does not meet your
posted on January 19, 2019 
Math
I will read it as: √(2t+1)  5 = √t √(2t+1) = 5  √t square both sides: 2t+1 = 25  10√t + t 10√t = 24  t square again 100t = 576  48t + t^2 t^2  148t + 576 = 0 (t  144)(t  4) = 0 t= 144 or t = 4, BUT since we squared the equation each of
posted on January 19, 2019 
Math
If after simplifying you end up with an x term , you will have one unique solution e.g. 3x + 9 = 24 3x = 15 x = 5 If after simplifying your x terms drops out and you end up with a true statement, your equation will have an infinite number of solutions.
posted on January 19, 2019 
Math
75 ≤ (73+82+73+77+77+b)/6 < 80 75 ≤ (382+b)/6 < 80 , should be obvious what I did 450 ≤ 382+b < 480 , I multiplied everybody by 6, in the middle that canceled the 6 at the bottom 68 ≤ b ≤ 98, I subtracted 382 from everybody and I am done! What
posted on January 19, 2019 
Math
You must know the properties of lines written in the form y = mx + b m is the slope of the line and b is the yintercept so for y = x + 4 that line should have a slope of 1, it should lean to the left making an angle of 45° with the xaxis it will have
posted on January 19, 2019 
Math
which graph ??
posted on January 19, 2019 
Math
75 ≤ (73+82+73+77+77+b)/6 < 80 carry on
posted on January 19, 2019 
algebra 2
A cube has a volume of 100 cm^3 How long is each of its sides ? x^3 = 100 take the cube root of 100, use your calculator
posted on January 18, 2019 
math
x  4 ≥ 1 x ≥ 3 So your graph should show a number line, with a solid "dot" on the 3 and the arrow going to the right. Where does the 10 come from? Does you line stop at 10?
posted on January 18, 2019 
Math
Most of your questions are basically the same. You have shown no indication where your difficulty with these problems lie in solving these little questions, and have made no effort to even show any attempt by you. What would you do for the above problem??
posted on January 18, 2019 
math
You are given three of the xintercepts of p(x) So in it simplest form p(x) = (x+3)(x+1)(x5) confirmation: https://www.wolframalpha.com/input/?i=plot+p(x)+%3D+(x%2B3)(x%2B1)(x5) other version could be p(x) = 14(x+3)(x+1)(x5) p(x) = (x+3)(x+1)(x5)(x+9)
posted on January 18, 2019 
Math
looks like b+5 = 29 b = 24 Not sure what the last part of the question is really getting at. Are they simply attempting to describe the process of solving my little equation? If so, then this is an example of how to "complicate a simple idea".
posted on January 18, 2019 
Math
Do not attach a new question as a response to a previous post, often it will not be viewed since tutors will think the question has been answered. As to the walking question, did you mean 2 1/6 km (as in "two and one sixth) ? If so.... what is 2 1/6  1
posted on January 18, 2019 
Math
total use = 3/4 + 4/5 + 3/4 = your LCD will be 20
posted on January 18, 2019 
math
Difference between 2 parts indicates subtraction of the 2 parts so 6z  z^6 or z^6  6z which could be stated as z^6  6z
posted on January 18, 2019 
Math
It is much more important to understand how you get that answer. Make a sketch of your triangle. The centroid is the intersection of all 3 medians of a triangle, two would be sufficient. A median of a triangle is a line running from a vertex to the
posted on January 18, 2019 
Math
What is 2*2*3 ? where * means multiplication.
posted on January 18, 2019 
Math
1/16x^2 + 1/3x + 4/9 you want that in the form (ax^2 + b)^2 look at the first term, it is a perform square, so more than likely you will have (1/4x + ?)^2 look at the last term, it is also a perfect square, so perhaps we have (1/4x + 2/3)^2 expand it to
posted on January 18, 2019 
algebra
clearly, 55h < 385 h < 7 So she obviously drove less than 7 hours, but we can't determine the actual time.
posted on January 17, 2019