Wednesday
May 4, 2016

Posts by Reiny

Total # Posts: 34,471

Math
If 1/4 inches ---> 1 ft then 1 inch -----> 4 ft and 3 inches ---> 12 ft
April 13, 2016

Math
Make a sketch, extend the line from the top of the tower to the man until it hits the base line You now have a small isosceles right-angled triange within a larger one. so the smaller one has legs 1.4 m and 1.4 m. So the base of the larger is 1.4+10 or 11.4 m, which means that...
April 13, 2016

Damon,steve,reiny,bobpursley....Any 1 just help me plz
That's just plain silly.
April 13, 2016

Geometry
You want the lateral surface area of a cone = π r s, where r is the radius, and s is the "slant" height = π(25)(32) = cm^2
April 13, 2016

Algebra
This is a GP where a = 26000 and r = 1.03 sum(5) = 26000(1.03^5 - 1)/(1/03-1 = $138,037.53
April 13, 2016

Algebra 2
if you want your index to be n = 0 , then 9 Σ 2(n+1) n=0
April 13, 2016

Algebra 2
10 Σ 2n n = 1
April 13, 2016

Probability
I did the first two for the last two , you are dealing with conditional probability Prob( B given A) = prob(B|A) = prob(A and A)/prob(A)
April 13, 2016

oops - Math
ignore my previous answers, I totally forgot about the actual probabilities. so for prob(makes first misses seconds and third shots) = (7/10)(3/10)(3/10) = 63/1000 or .063 prob(missing all 3) = (3/10)^3 = 27/1000 so prob(of making at least one shot) = 1 - 27/1000 = 973/1000...
April 13, 2016

Math
h -- hit m -- miss she has the following cases: hhh hhm hmh mhh hmm * mhm mmh mmm "makes first misses seconds and third shots " --- I see one case, marked with * so prob(hmm) = 1/8 "Makes at least 1 shot" all except mmm so prob(of that event) = 1 - 1/8 = 7/8
April 13, 2016

Math
No common ratio, thus no geometric sequence however the 2nd, 3rd and 4th form the pattern: -(consecutive even)^2 but then the first term does not follow this pattern. I don't see anything else
April 13, 2016

Trig
You should memorize the trig ratios is terms of x, y and r so for the point (-1,3) x = -1, y = 3 and by Pythagoras, r = √10 cosθ = x/r = -1/√10 and since secθ = 1/cosθ secθ = -√10
April 13, 2016

math
There are 3 such multiples, 6,12, and 18 prob(of your event) = 3/18 = 1/6
April 13, 2016

Math
Are we answering only c) ? c) since there are only reds and whites, and you want prob(red OR white) the prob(red OR white) = 1 that is, 2/10 + 8/10 = 10/10 = 1
April 13, 2016

Calculus Answer Confirming Not Sure Im Right Help?
For the given substitution , the two statements: lim (∛x-4)/(x-64) , as x --->64 and lim (u - 4)/(u^3 - 64) , as u ---> 4 are equivalent, so lim (∛x-4)/(x-64) , as x --->64 = 1/48 and lim (u - 4)/(u^3 - 64) , as u ---> 4 = 48 They are equivalent ...
April 12, 2016

Calculus Answer Confirming Not Sure Im Right Help?
let ∛x = u then x = u^3 and as x---> 64, u ---> 4 lim (∛x-4)/(x-64) , as x --->64 = lim (u - 4)/(u^3 - 64) , as u ---> 4 = lim (u-4)((u-4)(u^2 + 4u + 16) , u -->4 = lim 1/(u^2 + 4u + 16), as u --> 4 = 1/(16 + 16 + 16) = 1/48 When you make your ...
April 12, 2016

IMPORTIANT MATH
let the width be x let the length be y, along the wall so 2x + y = 75 y = 75-2x area = xy = 600 x(75 - 2x) = 600 -2x^2 + 75x = 600 x^2 - 37.5x = -300 x^2 - 37.5x + 351.5625 = -300 + 351.5625 (x - 18.75)^2 = 51.5625 x - 18.75 = appr 7.18 x = appr 25.93 y = 23.139
April 12, 2016

Math
I ask myself, "how far from the x-axis is my given angle" After I decide which quadrants the given angle is in, I go in II: 180 - angle in III: angle - 180 in IV: 360 - angle e.g. for 330° , which is in IV reference angle = 360-330 = 30° ... for 203, which is...
April 12, 2016

Math
area of yard = (14x)(19x) = 266x^2 area of circle = π(36x^2) area of remaining yard = 266x^2 - 36πx^2 = (266-36π)x^2
April 12, 2016

Math
let the monthly rate be i 614( 1 - (1+i)^-48)/i = 24905 (1 - (1+i)^-48)/i = 40.56189 that's toughie to solve, I will use Wolfram https://www.wolframalpha.com/input/?i=solve+614(+1+-+(1%2Bx)%5E-48)%2Fx+%3D+24905 i = .00709 so the annual rate compounded monthly = 12(.00709...
April 12, 2016

finance math
not that simple let the monthly rate be i 614 (1 - (1+i)^-48)/i = 24905 very tough to solve I will let Wolfram do it https://www.wolframalpha.com/input/?i=sove+614+(1+-+(1%2Bx)%5E-48)%2Fx+%3D+24905 i= .00709283 12i = .08511... or 8.511% per annum compounded monthly
April 12, 2016

algebra
amt = 800(1.02^22 - 1)/.02 = ....
April 12, 2016

Math question help!!
Two interpretations are possible for this question. 1. There are 24 students in the class like you said. So if 1/3 are missing, then there are 8 missing, just like Ms Sue had in her previous post. 2. With 1/3 missing, there are 24 students in the class, so the 24 students ...
April 12, 2016

math
Only A and B make sense although at the end of A , you probably meant to say 4 people at round table
April 12, 2016

Algebra
width --- x length --- 4x area = x(4x) = 36 4x^2 = 36 x^2 = 9 x = 3 the room is 3 m by 12 m
April 12, 2016

Algebra
smaller tile --- x by x larger tile ---- x+4 by x+4 x^2 + (x+4)^2 = 40 expand and solve as a quadratic equation. it will factor and solves easily.
April 12, 2016

Algebra
thoko ---x zandile -- x+4 4 years ago: thoko -- x-4 zandile -- x x(x-4) = 165 x^2 - 4x - 165 = 0 (x-15)(x+11) x = 15 or x = -11 state the conclusion
April 12, 2016

Algebra
".A student is 6 times younger than her teacher" --> usually stated as, teacher is 6 times older than the student age of student --- x age of teacher ---- 6x 3 years ago: student : x-3 teacher : 6x-3 (x-3)(6x-3) = 36 6x^2 - 21x + 9 - 36 = 0 6x^2 - 21x - 27 = 0 2x^...
April 12, 2016

finance
amount = 4000( 1.105^5 - 1)/.105 = ...
April 12, 2016

Algebra, math
Nothing as serious as when WKRP's Les Nessman reported live turkey's dropping from the sky. "As God is my witness, I thought turkeys could fly!!!" -- Arthur Carlson, WKRP in Cincinnati
April 12, 2016

math
let the unit digit be x let the middle digit be k let the hundred digit be y the original number = 100y + 10k + x the number reversed = 100x + 10k + y so 100x + 10k + y = 100y + 10k + x 99x = 99y x = y We sort of knew that so it doesn't matter what we put in the middle to ...
April 12, 2016

Trigonometry
a) if the cone is 8 inches high and it is filled with a depth of 8 inches, then the cone is full of water, and the radius of the water level must be 4 inches. Is there a typo here? b) let the height of the water be h, and the radius of the water level be r by similar triangles...
April 12, 2016

math
You are correct with A = w(w+3)
April 12, 2016

Math
first year -- 4 = 2(2^1) 2nd year ---- 8 = 2(2^2) 3rd year ---- 16= 2(2^3) can you see the pattern ... 10th year ----- 2(2^10) = 2048 you were right! Did you do it in a different way?
April 12, 2016

Math Help!
remember, when you divide powers with the same base, keep the base and subtract the exponents, so 7^9/7^3 = 7^9 ÷ 7^3 = ...
April 12, 2016

College Algebra
No idea what the Malthusian model is, but I will do it my way P = 30,000 e^(kt) , where k is constant and t is years given:when t = 9, P = 60,000 30000 e^(9k) = 60000 e^(9k) = 2 9k = ln2 k = ln2/9 P = 30,000 e^((ln2/9)t) when is P = 1,000,000 ? 30,000 e^((ln2/9)t) = 1,000,000 ...
April 12, 2016

Calculus I
V = (4/3)π r^3 dV/dt = 4π r^2 dr/dt given: dV/dt = 8π , r = 1 8π = 4π(1) dr/dt dr/dt = 8π/4π = 2 A = 4πr^2 ----> (did you notice that surface area equals the derivative of volume ??) dA/dt = 8πr dr/dt when r = 1 dA/dt = 8π(1...
April 12, 2016

Math Help!
You are very welcome
April 12, 2016

Math Help!
correct for both
April 12, 2016

Math Help!
I noticed in your first question you have 4^a. None of the choices would match that. It had to be 2a(a^2 + 4a) to get a correct answer from your choices. You are using the distributive property which is illustrated by a(b + c) = ab + ac you multiply the stuff sitting in front ...
April 12, 2016

Algebra
Let the completed job be represented by 1 The first crew worked for 2 days, so they did 2/7 of the job. This leaves 5/7 of the job to be finished by the combined work of the two crews rate of first crew = 1/7 rate of 2nd crew = 1/5 combined rate = 1/7 + 1/5 = 12/35 let the ...
April 12, 2016

Math
XXXXXX 000901 This follows your wording, but a number such as 000901 would be 901, making it a 3 digit number. Does you number have decimals? then how about 901.000 ? Otherwise your question makes no sense
April 12, 2016

Algebra
Did you translate the English into Math? I said: x^2 = 4x + 60 now you have a nice and simple quadratic which factors. x^2 - 4x - 60 = 0 solve for x, and take only the positive result
April 12, 2016

Math
You obviously have a ||gram WXYZ where angle X = 113 In any parallogram, the opposite angles are equal and adjacent angles add up to 180 I don't know what <XYZ= <YZW= <ZWX= is supposed to mean. If 3 angles are to be equal then you must have a rectangle, which ...
April 12, 2016

algebra
see here http://www.jiskha.com/display.cgi?id=1460427888 Give yourself a nickname, so we can keep track of the questions and avoid duplication.
April 11, 2016

EASY Pre-Algebra
the four offices are defined and distinct. e.g, you could not simply interchange the office of the secretary with the office of the chairman So you have a permutation, since the order matters. Words such as "committee, select, choose" usually imply a combination
April 11, 2016

Calculus Help Stuck Part 2?
careful: what happened to your x's in (x-4)/(4-x) ? What really happened is this (x-4)/(4-x) = -1(4-x)/(4-x) = -1[ (4-x)/(4-x) ] = -1[ 1 ] = -1 Any number divided by its opposite = -1
April 11, 2016

Calculus Help Stuck Part 2?
Step1 for me in any limit question is actually sub in the approach value If you get a real number, that's your answer, all done! so for x = 4, we get 0/0, ok, we got work to do step: if you get 0/0 for simple rational expressions like the above, IT WILL FACTOR. Sometimes ...
April 11, 2016

maths
cosa = 12/13 construct a right-angled triangle and use Pythagoras to find the sides 5, 12, and 13 since the cosine is + in I or IV, we have two cases: case1: in quad I sina = 5/13, cosa = 12/13 seca + sina = 13/12 + 5/13 = 229/156 case2: in quad IV sina = -5/13, cosa = 12/13 ...
April 11, 2016

interest rates computation
first investment --- x 2nd investment ----- 4x .07x + .13(4x) = 7965 solve for x
April 11, 2016

algebra
Follow the same steps I showed you in the previous post Same kind of problem.
April 11, 2016

algebra
looks like everything is referenced in terms of quarters, so start with : let the number of quarters be x dimes ---- x+138 nickels ---- 2x pennies ---- 14x + 28 Now that you have the NUMBER of coins defined, we go for the VALUE of those coins 25x + 10(x+138) + 5(2x) + 1(14x+28...
April 11, 2016

Math
total ages = 60 Generally, if the mode is 8 would mean there are more than one age of 8 suppose there are two with age 8, leaving 44 for the other 4 (11 for the average of the remaining 4) could have 9 and 13, and 8 and 14 so we could have: 8,8,8,9,13,14 or we could have: 8,8,...
April 11, 2016

Calculus
go to your other post further up
April 11, 2016

Calculus
at x = 5, we get 20/0 which is undefined The limit does not exist (we only have work to do if the limiting value produces 0/0)
April 11, 2016

Math
Haven't seen anybody use tables out of "handbooks" in over 30 years, .... amount = 9000(1.08^20 - 1)/.08 = 9000(45.7619643) ---> last number should be in your handbook = $411,857.68
April 11, 2016

Math
A blue car cannot be on either end. So we have to start and end with a red car. They must be parked this way RBRBRBR number of way to do this is R-B-R-B-R-B-R 4x3x3x2x2x1x1 = 144
April 11, 2016

Word problem middle school
This looks like a GP with a = 4 r = 1.5 so cost = 4 + 4(1.5) + 4(1.5)^2 = ... I will let you do the arithmetic
April 11, 2016

Bus. Math help!
So PV = 80,000 i = .085/12 = .0070833333.... n = 12(25) = 300 payment = x x(1 - 1.00708333..^-300)/.00708333...) = 80,000 x = 644.18 which is none of the choices, D would come closest
April 11, 2016

probability
let m be the mean, and let s be the standard deviation (11 - m)/s = -3 11-m = -3s (16-m)/s = 3 16-m = 3s add them : 27 - 2m=0 m = 13.5 3s = 16-13.5 = 2.5 Using my favourite normal distribution calculator: http://davidmlane.com/hyperstat/z_table.html I get .305
April 11, 2016

Math
C is correct
April 11, 2016

Calc
If (a,b) is a point not on Ax + By + C = 0 then the shortest distance D from (a,b) to the line is D = |aA + bB + C|/√(A^2 + B^2) First change your equation into general form: 4x - 2y - 4 = 0 D = |1(4) + (-5)(-2) - 4|/√(16+4) = 10/√20 = 10/2√5 = 5/√...
April 11, 2016

Math
I will go with your definitions then 2πr + 4s = 9 s = (9-2πr)/4 total area = A = πr^2 + s^2 = πr^2 + (9-2πr)^2 /16 dA/dr = 2πr + (1/8)(9-2πr)(-2π) = 2πr - π(9-2πr)/4 = 0 for a max/min 2πr = π(9-2πr)/4 8π...
April 11, 2016

Math
This question is not as easy as it first appears. John found the number of ways to select exactly 3 coins from the 5 given. But it said at least 3 coins so we could have 4 or all 5 number of ways to select = C(5,3) + C(5,4) + C(5,5) = 10 + 5 + 1 = 16 But we have not yet ...
April 11, 2016

Algebra 2
For each of the given trig ratios, make a sketch of the corresponding right-angled triangles sinα = 12/13 , so y = 12, r = 13 x^2 + y^2 = r^2 x^2 + 144 = 169 x^2 = 25 x = 5 in quad I , so sinα = 12/13 , cosα = 5/13 cosβ = 21/29 in quadrant I x = 21, r=29 y...
April 11, 2016

math
Just do it. The instructions are quite clear.
April 11, 2016

algebra
for y = ax^2 + bx + c the x of the vertex is -b/(2a) so for yours, the x of the vertex = 16/8 = 2 I see (2, -7) as the only point where x = 2 I would now sub x = 2 into the equation to make sure I get -7
April 11, 2016

Algebra 2
Steve, as long as they are not imaginary.
April 11, 2016

math
The letters: AA RR NN G EE M T Number of arrangements = 11!(2!2!2!2!) = 2,494,800
April 11, 2016

math
let the number of students be 19x let the number of teachers be x 19x + x = 500 20x = 500 x = 25 There are 19(25) or 475 students and 25 teachers check: total = 25+475 = 500 ratio = 475 : 25 = 19:1
April 11, 2016

calculus
h = -16t^2 + 79t + 4 we need the vertex of this downwards parabola the t of the vertex = -b/2a = -79/-32 = 79/32 sec for that time height = -16(79/32)^2 + (79/32)(79) + 4 = 197.796.. = 197.80 correct to 2 decimals check my arithmetic
April 11, 2016

Math HELP PLEASE QUICK!
3.54x10^7 m /(3x10^8 m/s) = .118 seconds
April 11, 2016

Calculus
I will assume that you had y'' = 2(x-12)/x^4 f(x) will be concave up when y" > 0 and concave down when y" < 0 we don't have to worry about x^4, it will always be positive, except when x = 0 , which is a restriction on f(x) anyway. I don't see ...
April 11, 2016

Calculus
f(x) = ax^3 + cx^2 + d f'(x) = 3ax^2 + 2cx + 0 f'(-4) = 9 48a - 8c = 9 ** the point (-4,9) is on f(x) -64a + 16c + 6 = 9 *** 2 times ** ---> 96a - 16c = 18 *** ---------> -64a + 16c = 3 add them: 32a = 21 a = 21/32 in 48a - 8c = 9 48(21/32) - 8c = 9 -8c = -45/2 c...
April 11, 2016

mathematics-root of cubic eqn
let f(x) = x^3 + 2x^2 + 3x - 4 by trial: attempt x = ±1 , ±2, ±4 f(1) = 1+2+3-4 ≠ 0 f(-1) = -1+2-3-4 ≠ 0 f(2) = 8+8+6-4 ≠ 0 f(-2) = -8 + 8 - 6 - 4 ≠ 0 f(4) ≠ 0 f(-4) = -64 + 32 - 12 - 4 ≠ 0 There are no nice rational ...
April 11, 2016

Math
The 300 would be correct if he gave no discount So his final selling price has to be P300 let the marked price be x so .6x = 300 x = 300/.6 = 500 check: the marked price is 500 giving a discount of 40%, which is 200 means that he sells at 300 profit = 300-200 = 100 percentage ...
April 11, 2016

Math
distance of 1st bounce --- 8 distance of 2nd bounce --- 2(4) = 8 distance of 3rd bounce --- 2(2) = 4 distance of 4th bounce --- 2(1) = 2 distance of 5th bounce --- 2(1/2) = 1 distance of 6th bounce --- 2(1/4) = 1/2 distance of 7th bounce --- 2(1/8) = 1/4 distance of 8th bounce...
April 11, 2016

@ Anonymous
If you are going to give a detailed solution, then you should not gloss over the critical part of your solution: SO Equation 1 X + (6/X) = 5 X=2 or else you might just as well state the obvious solution at the beginning.
April 11, 2016

math
2 and 3 just sort of popped into my mind.
April 11, 2016

Math
Your distance of 450.69 miles is correct However, the angle of 17.43 is the angle within the triangle. You must add the original direction of 27 degrees to get S 44.3 E
April 11, 2016

Math
After you make your sketch, and after you enter your angles, you should realize that the plane makes a 90 degree turn. So you just have a right-angled triangle. Use Pythagoras to find the distance. Let the angle opposite the 135 side be θ then tanθ = 135/430 θ...
April 11, 2016

Math: Trigonometry
ahhh, missed the part where we want the sum of the first 3 π/12 + 5π/12 + 7π/12 = 13π/12
April 10, 2016

Math: Trigonometry
4cos^2(2x-pi) = 3 cos^2 (2x - pi) = 3/4 cos (2x-pi) = ± √3/2 I know that cos 30° = √3/2 so 2x - pi = pi/6 2x = pi + pi/6 x = 7pi/12 ---->105° since we had cos(2x-pi) = ± √3/2 2x - pi could have been in any of the 4 quadrants 2x - pi...
April 10, 2016

Geometry
simplest way: Heron's Formula A = √(s(s-a)(s-b)(s-c)), where s = (1/2)the perimeter. s = (1/2)(15 + 15 + 8) = 19 s-a = 19-15 = 4 s-b = 19-15 = 4 s-c = 19-8 - 11 area = √(19(4)(4)(11) = √3344 = appr 57.83 2nd way: works in this case because it is isosceles...
April 10, 2016

math
First let's choose the books top shelf = C(6,4) = 15 middle shelf = C(3,2) = 3 bottom shelf = C(6,3) = 20 so he can read 15x3x20 or 900 different combinations of 9 books Now for each of the choices of 9 books, he can read them in 9! ways. so the number of ways he can read ...
April 10, 2016

math
ahh, behold the beauty of the metric system 130 mm = 13 cm
April 10, 2016

Math
Don't know what you mean by "I had to make prisms out of construction paper of the same size". Did you mean the same volume? , the same height? What stays the same?
April 10, 2016

Trig
you need to sketch right-angled triangles to get the missing sides given: sinx = -1/4, y = -1, r = 4 x^2 + y^2 = r^2 x^2 + 1 = 16 x = -√15 in III So sinx = -1/4 , cosx = -√15/4 , tanx = 1/√15 given: cosy = -4/5, x = -4, r = 5 then y = -3 siny = -3/5, cosy = -...
April 10, 2016

algebra
So this flagpole is almost 4 miles high? WOW And the cables are attached almost 2 miles from the base of this massive flagpole?? Check your typing, I bet you dropped a decimal point or something.
April 10, 2016

Math
Other than the fact that you can't bushwhack on the Appalachian Trail, we have a clear cut case of using the cosine law: let the distance back be x miles x^2 = 8^2 + 10^2 - 2(8)(10)cos113° = 273.40... x = 16.534.. (don't round off your calculator answer) now by the...
April 10, 2016

Math
#1, correct #2, to be horizontal, they must have the same y to be vertical, they must have the same x So, do you wish to change your answer?
April 10, 2016

Math
assuming that numbers and letters can be repeated ... number of cases = 26x10x10x10x26 =
April 10, 2016

Trigonometry
for each one, use the CAST rule to find where else a certain trig ratio is positive or negative for #1, you have found the angles in quadrant I, but the tangent is also positive in III, (the T of CAST) So è = 30 degrees in I ---> pi/6 or è = 210 in III ------ ...
April 10, 2016

interest
no time given for the first part. 2nd part: 500(1.04)^n = 1000 1.04^n = 2 take log of both sides n log 1.04 = log 2 n = log2/log1.04 = 17.67 years or n = 17.7 years correct to one decimal
April 10, 2016

Geometry
confusing question. Where does A come from. your 4 points R,S,T,U do not form a parallogram What are Rec1 etc ?
April 10, 2016

math
I know that Sixteen tons will get you another day older and deeper in debt
April 10, 2016

Math
Just did this less than an hour ago http://www.jiskha.com/display.cgi?id=1460275337
April 10, 2016

Maths
volume = pi r^2 h plug in your numbers, your r = .8
April 10, 2016

Math
a) for 25 therms cost = $.6686(25)) = $16.72 b) cost = 16.72 + (45-25)(.8587 = $33.89 c) cost = (x-25)(.8587) + 16.72 , for x > 25 or = .6686x , for 0 < x ≤ 25
April 10, 2016

math
morning of day 1 -- 3 ft evening of day 1 -- 1 ft ,(3-2) morning of day 2 -- 4 ft evening of day 2 -- 2 ... morning of day 27 -- 29 ft evening of day 27 -- 27 ft morning of day 28 -- 30 ft He has reached the top, no sliding back He will reach the top on Feb 28th
April 10, 2016

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