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 
Kelly, Justie, Nicole, Keisha
Please settle on one name
asked on October 22, 2013 
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
Let t hours be any time after noon Make a sketch of that position. Let the distance between them be D miles I have a rightangled triangle and D^2 = (15t)^2 + (4012t)^2 2D dD/dt = 2(15t)(15) + 2(4012t)(12) when t = 1, D^2 = 15^2 + 28^2 D = √1009 then
posted on November 14, 2018 
Math
The question asked for the rounded answer to the nearest 10 dollars. $627.58 to the nearest $10 is $630 , which is not in your list of answers.
posted on November 14, 2018 
Math
No dimensions given for the rectangular prism, so I can't do the problem. However, the volume of the full cone = (1/3)π(12^2)(9) cubic inches = 432π cubic inches So the volume when the water is 4.5 inches high and has a radius of 6 inches (similar
posted on November 14, 2018 
Math
let the number of hours when the cost is the same by h hours 16h = 11h + 5 solve for h
posted on November 14, 2018 
Math
4x^2  x = 0 x(4x  1) = 0 x = 0 OR 4x  1 = 0 x = 0 or x = 1/4
posted on November 14, 2018 
Math
I am going to expand the expression, then use the formulas for ∑ n^3, ∑ n^2, etc ∑ (k^4)  (k4)^4 for k = 1 to n = ∑ k^4  (k^4  16k^3 + 96k^2 256k + 256) for k = 1 to n =∑ 16k^3  96k^2 + 256k  256 for k = 1 to n = 16( n(n+1)/2 )^2 
posted on November 14, 2018 
Geometry
Ummmhhh, wouldn't they form a straight line? So ...
posted on November 13, 2018 
Algebra
What they want you to do: #1 ..... 3=9x−2y 2y = 9x  3 y = (9/2)x  3 > slope = 9/2 #2 ..... 8=mx+3y mx  8 = 3y (m/3)x  8/2 = y > slope = m/3 but they are perpendicular, so m/3 = 2/9 solve for m
posted on November 13, 2018 
Math
speed of car  x km/h speed of lorry  x20 km/h time taken by car = 280/x hrs time taken by lorry = 280/(x20) hrs. 1 hour and 10 minutes = 1 + 10/60 = 7/6 hrs 280/(x20)  280/x = 7/6 multiply each term by 6x(x20) 280(6x)  280(6(x20)) = 7x(x20)
posted on November 13, 2018 
Math
average width of a book = 150/60 cm = .... then number of books for 80 cm = 80/width of book or just use a simple ratio n/80 = 60/150 , solve for n , the number of books
posted on November 13, 2018 
math
Let's use the simple formula: shortest distance between the point (p,q) and ax + by + c = 0 is ap + bq + c / √(a^2 + b^2) pick any point on y = (1/3)x + 2, say (3,3) change the second equation to the general form ax + by + c = 0 and apply the formula I
posted on November 13, 2018 
algebra
Pick an x, any x. I will pick x = 1 then g(1) = 2(1)  3 = 5, so we have a point (1,5) pick another x, any x, I will pick x = 3 g(3) = 2(3)  3 = 3, so we have another point (3,3) plot them, join with a line, extend the line, all done !
posted on November 13, 2018 
Calculus
First reduce and change 12x+12y=2 to 6x + 6y = 1 Doing it another way: slope of this line is 1 so the slope of the perpendicular is +1 and the line passing through the origin with slope 6 is y = x sub into the given line 6x + 6y = 1 6x + 6x = 1 x = 1/12 y
posted on November 13, 2018 
math
80 < (84+90+x)/3 < 90 240 < 174+x < 270 66 < x < 96
posted on November 13, 2018 
Trig
y= 2+7csc(3x6) csc(3x6) = (y+2)/7 or sin(3x6) = 7/(y+2) construct a rightangled triangle with angle (3x6), opposite side 7, and hypotenuse Y+2 then x^2 + 49 = (y+2)^2 x = √((y+2)^2  49) cos(3x6) = √((y+2)^2  49) / (y+2) sec(3x6) = (y+2)/
posted on November 13, 2018 
Math
I did one similar to this here: https://www.jiskha.com/questions/1778715/AddthefollowingvectorsusingtheComponentlawa9msN30Eand2msN
posted on November 13, 2018 
Math
I assume that you know that the slope of 2x + 5y – 3 = 0 is 2/5 by just looking at it. Then the slope of the new line must be 5/2 and its equation must be 5x  2y + c = 0 . Plug in the given point to find c.
posted on November 13, 2018 
Math
For your given vector equation (x, y) = (3, 8) + t(3, 2) the parametric equation would be x = 3  3t y = 8  2t Form the new equation. Keep in mind that, since it is parallel to the above, the direction must be the same
posted on November 13, 2018 
math
N30°E > 60° in standard notation N 60°E  > 30° so .... I read 9 m/s [N30°E] and 2 m/s [N 60°E] as (9cos60°, 9sin60°) + (2cos30°, 2sin30°) = (9(1/2), 9(√3/2) ) + (2(√3/2), 2(1/2) ) = .... do b) in the same way
posted on November 13, 2018 
linear differential algebra
(2D+3)(x)(D+3)(y) = 5 times (D+1) > (D+1)(2D+3)(x)(D+3)(D1)(y) = 5(D1) (D+1)(2D+3)(x) + (D^2 + 4D + 3)y = 5D  5 ** (D+1)(x)  (2D+5)(y) = 7+4t times (2D+3) > (D+1)(2D+3)(x)  (2D+5)(2D+3)(y) = (7+4t)(2D+3) (D+1)(2D+3)(x) + (4D^2 
posted on November 13, 2018 
math
Try this: https://www.youtube.com/watch?v=dBMksZGU6eU
posted on November 13, 2018 
Math
mandays needed = 5(26) = 130 So 10 men should be able to it in .....
posted on November 13, 2018 
math
Check to see that the value of r = 3/2 , that is ... (4/27) ÷ (8/81) and (2/9) ÷ (4/27) = 3/2 so a = 8/81, and r = 3/2 sum(n) = a(1  r^n)/(1r) sub in the values and evaluate, let me know what you got
posted on November 13, 2018 
Maths
https://www.purplemath.com/modules/triggrph3.htm
posted on November 13, 2018 
Math
The differences between consecutive pairs: 0,1,2,3,4,... which means the second differences are: 1,1,1,1,... Thus it can be expressed as a quadratic function I got this by: let the function be y = ax^2 + bx + c and subbed in the points (1,1), (2,1), (3,2),
posted on November 12, 2018 
Math
the answer is correct, but you must include the restrictions which are : x ≠ 0, 2, 3 Why do you need the steps explained ? If you don't know, how did you get the answer ????
posted on November 9, 2018 
math
So gallons of water = 7.2(10^4)(2900) or 208,800,000 gallons = 2.088(10^8) this is also equal to 2.088(10^x) So if 2.088(10^x) = 2.088(10^8) clearly, x must be 8 notice, no calculator was really required other than (7.2)(10^4)(2900)
posted on November 9, 2018 
6th grade Math
I agree with all of your answers
posted on November 9, 2018 
Math
Since the new line is to be parallel to the given one y = x  2 it will differ only in the constant at the end. let the new one be y = x + b sub in the point (2, 2) and you will find the value of b Give it a try, let me know what you got
posted on November 8, 2018 
math
for functions like y = a sin(kx) and y = a cos(kx) the amplitude is a, that is, y lies between a and +a and the period is 2π/k so for yours 2π/k = 60 k = 2π/60 = π/30 we are also supposed to have f(0) = 8, so it could be a cosine function f(x) =
posted on November 8, 2018 
Math
yes, that's why I wrote it as (cos(3x))^2 , so you would see it that way
posted on November 8, 2018 
Math
could just go from: lim 2sin2x/3cosx as x> 0 = 2(0)/(3(1)) = 0/3 = 0
posted on November 8, 2018 
Math
have you seen sin(A+B) = sinAcosB + cosAsinB ??? then sin (2A) = sin(A+A) = sinAcosA + cosAsinA = 2sinAcosA, called the double angle formula.
posted on November 8, 2018 
Math
lim as x approaches 0 (e^4x1)/sin(2x) assuming you mean: (e^(4x)  1)/sin(2x) = lim (4 e^(4x))/(2cos(2x)) as x > 0 = 4e^0 / 2cos0 = 4(1)/2 = 2
posted on November 8, 2018 
Math
sin(2A) = 2sinA cosA, one of the standard identities.
posted on November 8, 2018 
Math
derivative of 1  cos^2 (3x) = derivative of 1  (cos(3x))^2 = 2cos(3x) (3)(sin(3x) = 3(2sin(3x)(cos(3x)) = 3sin (6x)
posted on November 8, 2018 
Math
using L'Hopital's rule lim (1cos(2x))/(3sinx) as x > 0 = lim 2sin2x/3cosx = 4sinxcosx/3cosx = (4/3)sinx , as x > = 0
posted on November 8, 2018 
Math
Not a very realistic question, but it can be solved mathematically. let the time taken be t hrs. 9t + 6t = 20 t = 20/15 hrs or 80 minutes.
posted on November 7, 2018 
Math
oops , let's try that again, should write these out first. assuming you meant: (2x+2)/(3x^2+6x+3)+ (x7)/(3x^23) = 2(x+1)/((3)(x+1)(x+1)) + (x7)/(3(x+1)(x1)) LCD is 3(x+1)(x+1)(x1) = ( 2(x+1) + (x7)(x+1) )/( (3(x+1)(x+1)(x1) ) = (2x+2 + x^2  6x 
posted on November 6, 2018 
Math
After many reminders for past posts, you must know by now that brackets are critical for these type of problems, so (2x+2)/(3x^2+6x+3)+x7/(3x^23) = 2(x+1)(3)(x^2 + 2x + 1)/(3(x^2  1)) = 6(x+1)(x+1)(x+1)/(3(x+1)(x1)) = 2(x+1)^2 /(x1) , x ≠ ±1
posted on November 6, 2018 
math
Did you make a sketch of 2 intersection straight lines? What is meant by "union" ?
posted on November 6, 2018 
Math
none of them are irrational 1.414213562 = 1,414,213,562/1000,000,000 = 707,106,781 / 500,000,000 so c) is rational a) is not even a number
posted on November 6, 2018 
Calculus HELP
as x> 0 from the left, you get −∞ as x> 0 from the right, you get +∞ see graph: http://www.wolframalpha.com/input/?i=plot+y+%3D+1%2Fx
posted on November 6, 2018 
Calculus HELP DAMON
Since it is a linear function, that is, it can be represented by a straight line, they are the same. The slope of the line is constant, so it is the same whether you take an average, or take the instantaneous rate of change.
posted on November 6, 2018 
Math
Back to the question: the area of .... 200 m by 75 m = 15,000 m^2 or 1.5 x 10^4 m^2 if written in scientific notation. the closest that comes to that is the improperly typed c)
posted on November 6, 2018 
history
What does your text say? Did you read it? If you can't find the answer there, look at this: https://www.historytoday.com/stellaghervas/whatwascongressvienna
posted on November 6, 2018 
Financial
I will assume that the rate is 5.35% per annum, compounded monthly, that is i = .053/12 = .0041666.. let the balloon payment be x 925(1.0041666..^360  1)/.0041666... + x = 235,000(1.004166...)^360 solve for x Tell me what you got. If you get an answer of
posted on November 6, 2018