Wednesday
August 24, 2016

Posts by Reiny

Total # Posts: 35,548

Math
grandma's age --- 10x + y mother's age ---- 10y + x one year ago: grandma : 10x+y - 1 mothers: 10y+x - 1 10x+y - 1 = 2(10y+x-1) 10x + y - 1 = 20y + 2x - 2 8x - 19y = -1 8x = 19y-1 x = (19y-1)/8 try different y's so that the numerator is a multiple of 8 e.g. when y...
May 22, 2016

Pre-Calc
Prob(3 or 4 are aces) = ( C(4,3)C(48,2) + C(4,4)C(48,1) )/ C(52,5) = ....
May 22, 2016

Math
Each pear costs $4 more than each Apple --- p = a + 4 Now , that's some expensive fruit !! 6a = 4p 6a = 4(a+4) 6a = 4a + 16 2a = 16 a = 8 , then p = 12 An apple costs $4 and a pear costs $12 WOW, but the answers check out for you info
May 22, 2016

Math
What is 4000(1.01025)^60 ?
May 22, 2016

algebra
Trying to make sense out of the gibberish English. I will assume you meant: How old will her daughter be when her age is 1/3 of her mother's age. daughter now : ---- 0 mother now -------21 0+x = (1/4)(21+x) 4x = 21 + x 3x = 21 x = 7 Find their ages in 7 years, and see if ...
May 22, 2016

Math
original numbers: x and y original product : xy new numbers: .75x and .5y new product = .375xy or (3/8)xy change in product = (5/8)xy percentage change = (5/8)xy/(xy) = 5/8 = .625 = 62.5 %
May 22, 2016

Maths
(3/4)x + (1/7)x + 27 = x times 28 21x + 4x + 756 = 28x at this point I can tell that he spent 25/28 of his money and he would have 3/28 of it left over 25x + 756 = 28x 3x = 756 x = 252 state you conclusions
May 22, 2016

MATHS
wouldn't that have to be 76479 ?
May 22, 2016

Pre-Calc
Prob(3 hearts) = C(13,3)/C(52,3) = 286/22100 = .0129 yes
May 22, 2016

maths
clock #1 runs at (29/30)t relative to real time clock #2 runs at (61/60)t relative to real time (61/60)t - (29/30)t = 10 times 60 61t - 58t = 600 3t = 600 t = 200 minutes or 3hours, and 20 minutes which would make it 9:30 am
May 22, 2016

Mathematics
(...7)(...7) ends in 9 (.....9)( .... 7) ends in 3
May 22, 2016

Math
Aaron ---- x his dad --- 9x One year ago: Aaron --- x-1 his dad --- 9x-1 9x-1 = 11(x-1) + 2 9x - 1 = 11x - 11 + 2 8 = 2x x = 4 Aaron is 4 dad is 36 one year ago Aaron -- 3 dad ---- 35 ---> was he 2 more than 11 times 3 ?? YES
May 22, 2016

Math
monthly rate = .0585/12 = .004875 outstanding balance = 22350(1.075) - 1200 = 22826.25 interest for 1st month = 22826.25(.004875) = 111.28 amount going to principal = 475.25 - 111.28 = $363.97
May 21, 2016

math
first piece ---- x 2nd piece ---- 12-x I will assume the second piece is 3/2 inches longer than the first piece 12-x - x = 3/2 12-2x = 3/2 24-4x = 6 4x = 18 x = 4.5 first piece is 4.5 2nd piece = 12-4.5 = 7.5 So, what do you think?
May 21, 2016

Addition to .. - logarithm math-need help!!!!
My equation near the end should have included: 5 log 4 x + 48log x 4 = x/8 5 log4 x + 48/log4 x = x/2 or 5log 4/log x + 48log x/log 4 = x/2 btw, that is what I used in Wolfram , so my answer stands as is
May 21, 2016

logarithm math-need help!!!!
5logxbase4+48log4basex=x/8 ---> 5 log 4 x + 48log x 4 = x/8 One of rules of logs: log a b = 1/log b a and furthermore: log a b = log b/log a so 5 log 4 x + 48log x 4 = x/8 I don't know of any nice method to solve this, I ran it through Wolfram and got x = 2130.13 , ...
May 21, 2016

Math
This same question was recently in the news http://www.iflscience.com/editors-blog/can-you-solve-math-problem-went-viral-japan the way it was written by Jerry the answer would be 9
May 21, 2016

Algebra
Since you are putting the marble back, the prob of the second event is the same as the first one. Prob(red,red) = (2/10(2/10) = 1/25
May 20, 2016

math
What is the meaning of the "x" between the two equations? is the second equation 3y = 13 ? Then y = 13/3, which does not show up in any of your choices.
May 20, 2016

HELP ON MATHHHH!!!!
I think you want something like 3x - 4 ≤ 15 then 3x ≤ 19 x ≤ 19/3 If this is what you meant then the values from your set that would work are: { 0, 3, 5, 6} Make suitable adjustments to my my solution of you meant something other than ≤
May 20, 2016

Math Help!
#1, correct #2. Volume of any solid that comes to a point: V = (1/3) base x height = (1/3)(24^2)(24) = 1/3(24^3 = 4608
May 20, 2016

nawal
You should make a point to memorize the ratio of sides of the 30-60-90° triangle, which is 1 : √3 : 2 so for yours: √3/1 = √6/x √3x = √6 x = √2 then the hypotenuse = 2√2 area = (1/2)base x height =(1/2)(√2)(√6) = (1/2...
May 20, 2016

math
Just set up a simple ratio: 60/1.5 = 100/t
May 20, 2016

math
nothing found in the coefficients. for the m's --- > m^6 for the n's ----> n so GCF = m^6 n
May 19, 2016

Math Trigonometry
I made a sketch with Chicago as C, A as the end of the first flight, and B as the end of the 2nd flight. In triangle ABC AC = x, AB = 150, BC = 195, angle A = 65° by the sine law: sinC/150 = sin 65/195 sinC = .69715... C = 44.199... (I stored that in calculator's ...
May 19, 2016

math
Did you not read Steve's answer to your previous question regarding the condition to have a triangle? http://www.jiskha.com/display.cgi?id=1463702386
May 19, 2016

Algebra
number of .15 increases ----- n price per bushel = 5 + .15n number of bushels sold = 1000 - 10n income = (5+.15n)(1000 - 10n)
May 19, 2016

math
yes
May 19, 2016

math
let each of the straights be x m then the perimeter is 2x + 2half-circles = 2x + circumference of 1 circle 2x + 2π(35) = 400 solve for x
May 19, 2016

College Algebra
pounds of $8 nuts ----- x pounds of other nuts ---- 41-x 8x + 2(41-x) = 7(41) solve for x
May 19, 2016

Math
2^x=17 take log of both sides, then use log rules x log2 = log 17 x = log17/log2 = appr 4.087 4log4^(x)=7 log 4^x = 1.75 4^x = 10^1.75 4^x = 56.23413... repeat the same steps I used in the first one to finish it
May 19, 2016

Algebra 2
find the z-score for 140, then use your tables or charts or some software to find that .1587 will pass so number of the 360 that will pass = .1587(360) = 57 rounded to the nearest person
May 19, 2016

Trig
If sinØ = 3/7, y=3 , r = 7 and x^2 + 3^2 = 7^2 x = ± √40 Ø could be in I or II if Ø is in I sinØ = 3/7 cosØ = √40/7 cos(π/2 - Ø) = cos π/2 cosØ + sin π/2 sinØ = 0 + sinØ = 3/7 If &...
May 19, 2016

Algebra
y = -2/5x + 3 multiply each term by 5 , the LCD 5y = -2x + 15 get the x's and y's to one side, the constant to the other 2x + 5y = 15 None of your choices are correct. e.g. for y = (-2/5)x + 3 , (the original) the y-intercept is (0,3) (0,3) does not satisfy any of the ...
May 19, 2016

math
Assuming the 2 bags are distinguishable. then : C(5,1)xC(4,4) + C(5,2)xC(3,3) + C(5,3)xC(2,2) + C(5,4)xC(1,1) = 5 + 10 + 10 + 5 = 30 notice that this is row 1 5 10 10 5 1 of Pascal's triangle with out the leading and ending 1's. If the 2 bags are indistinguishable, ...
May 19, 2016

algebra 1
You want to find: −16t^2 + 90t + 50 = 28 + 48.8t 16t^2 -41.2t - 22 = 0 by the formula: t = (41.2 ± √3105.44)/32 = appr 3.03 or -.454 so you are correct, it is between 3 and 4, much closer to 3 seconds
May 19, 2016

Math
Flaw in problem: Two persons mentioned, but 3 terms in the ratio
May 19, 2016

Calculus
The way you worded the question, "How quickly is it moving away from the observer at that moment" , implies to find the rate at which the distance between the balloon and the observer changes. So we could just use Pythagoras after t sec, height of balloon is 8t ft so...
May 18, 2016

Algebra 2
I have to know more about the spinner. How many colours, etc
May 18, 2016

Algebra
nope, it is 4 units up Make a table of values of each using the same x's and see what happens http://www.wolframalpha.com/input/?i=plot+y%3D+-6+x%5E2+%2B4+,+y%3D+-6x%5E2
May 18, 2016

alg 2
the centre of (x - 2)^2 + (y + 1)^2 = 16 is (2,-1) Now move that centre 4 units to the left and 6 units up New centre is ....... new equation is .......
May 18, 2016

Calculus
a = 1.1+2(t^1/2) v = 1.1t + (2/(3/2)) t^(3/2) + c v = 1.1t + (4/3)t^(3/2) + c when t = 0 , v = 0 0 = 0 + 0 + c -----> c = 0 v = 1.1t + (4/3) t^(3/2) when t = 9 v = 1.1(9) + (4/3) (9)^(3/2) = 9.9 + (4/3)(27) = 9.9 +36 = 45.9 m/h
May 18, 2016

math
expression "2n+1" is your "number pattern" what do you get when you plug in n = 1, 2, 3, ... ?
May 18, 2016

gscc
height of cone is 1/2 the diameter ---> height of cone equals its radius V= (1/3)π r^2 h, but r = h V = (1/3) π h^3 dV/dt = π h^2 dh/dt *** dV/dt = 200 cm^3/s so when t = 10 V = 2000 cm^3 2000 = (1/3)π h^3 h^3 = 6000/π h = (6000/π)^(1/3) = appr...
May 18, 2016

math
4^x = 2^(2x) = (2^x)^2 let y = 2^x , so your equation becomes y^2 - 9y = -20 y^2 - 9y + 20 = 0 (y-4)(y-5) = 0 y = 4 or y = 5 then 2^x = 4 = 2^2 x = 2 or 2^x = 5 take log of both sides, and use log rules x log2 = log5 x = log5/log2 = appr 2.322
May 18, 2016

Math
20 evens, and 20 odds prob(E,E) = (20/40)(19/39) = 19/78
May 18, 2016

Inequality
-2 < 7-3x ≤ 10 subtract 7 from everybody -9 < -3x ≤ 3 divide everybody by -3, must switch inequality sign 3 > x ≥ -1 -1 ≤ x < 3 so integral values are {-1, 0, 1, 2}
May 18, 2016

Math
Wow, I don't see a single one of your answers. How can I possibly check them?
May 18, 2016

Math
To have the same colour, you need either BBB or RRR Find the prob of each case, then add them up
May 18, 2016

Math
If passing math depends on this ONE question, and you don't know how to answer this simple question, I don't think you should pass.
May 18, 2016

Math
prob(at least 1 boy of 4 kids) = 1 - prob(all girls) = 1 - (1/2)^4 = 1 - 1/16 = 15/16
May 18, 2016

Math/Applied
For the sum to be odd, one choice must be even , the other odd (the sum of two odds is even, the sum of 2 evens is even) We have 5 odds and 4 evens in the bag so 2 cases: prob(E, then O) = (4/9)(5/8) = 20/72 = 5/18 prob(O, then E) = (5/9)(4/8) = 5/18 prob(your event) = 5/18+5/...
May 18, 2016

Math
missing 3 times out of how many tries?? if prob(miss out of 3 tries) = (1/10)^3 = 1/1000
May 18, 2016

Math
looks like somebody has some major studying ahead of them
May 18, 2016

Math
I copied your post with only those that are INCORRECT I am using <-------- to show the correct answer 1. Simplify. 3x^2+ 5x-5x^2-4x+5-2 A.-8x^2-9x+3 B.2x^2+x+3 C.-2x^2-9x+3*** D.-2x^2+x+3 <--------- 4.The distance from Newtown to Old town on the highway is (6x^2 + 2x &#...
May 18, 2016

Math
Any reason why you are capitalizing every word? Assuming your garbled last sentence is something like: "If one of the sides of the first triangle is 6 cm, what is the length of the corresponding side of the second triangle ? " Areas of similar triangles are ...
May 18, 2016

Differential Calculus
Make a sketch of the cone with some water in it. Let the depth of the water be h ft, and the radius of the water level be r ft by similar triangles: r/h = 3.75/15 3.75h = 15r h = 4r or r = h/4 V = (1/3)π r^2 h V = (1/3)π(h^2/16)h V = (1/48)π h^3 dV/dt = (1/16)&#...
May 18, 2016

Calculus
take the 2nd derivative, set it equal to zero and solve for x that will be the x value of the inflection point, sub it back into the original equation to get the y your second derivative will be a linear expression, thus easy to solve for x
May 18, 2016

Math
you have 6 pizzas, and you slice each one of them into 5 pieces. How many pieces will there be in total ?
May 18, 2016

math
Find the area of the rectangle. Find the area of the circle take the difference between the two answers.
May 18, 2016

financial management
i = .16/12 = .013333... p(1 - (1.013333..)^-12)/.01333.. = 250000 solve for p , where p is the monthly installment
May 18, 2016

Math
area of parallogram = base x heigh = 6.5(4.8) = .. new dimension: base = 13 height = 6.3 new area = 13(6.3) = .... take the difference
May 17, 2016

Algebra
y = kx plug in the given values of x and y, then solve for k rewrite the original equation, now that you know k
May 17, 2016

math
(1/2)(l) = 2/3 l = (2/3) ÷ (1/2)
May 17, 2016

math
(sum of 4 tests + x)/5 = 77
May 17, 2016

Math3(Reiny Please Help)
h(t) - -9.81t^2 + 0t + h = 0 when it hits the ground when t = 3.5 -9.81(3.5)^2 + h =0 h = 120.1758 m b) repeat for the equation h(t) = -9.81t^2 -5t + 120.1725 set that equal to 0 and solve for t , reject any negative values of t
May 17, 2016

Math2(Reiny Please Help)
set 0.02(3s^2 + 20s) = 50 3s^2 + 20s = 2500 3s^2 + 20s - 2500 = 0 Use the quadratic formula, reject the negative answer.
May 17, 2016

Math(Reiny Please Help)
let the width against the barn be x ft let the length parallel to the barn be y ft so total length = 600/15 = 40 so she needs to fence 40 ft 2x + y = 40 y = 40-2x area =xy = x(40-2x) = 40x - 2x^2 are you taking Calculus? if so, d(area)/dx = 40 - 4x = 0 for a max of area x = 10...
May 17, 2016

Math
a) number greater than 9: 10,11,12,13,14,15 so 6 of them prob(as stated) = 9/15 = 3/5 b) do it the same way, count how many are prime, and how many are composite
May 17, 2016

Math
areas of similar figures are proportional to the square of their corresponding sides so the larger one is 9 times as large, or 243 m^2 or, if you didn't know that property let the original be (1/2)(base)(height) = 27 new one is (1/2) (3base)(3height) = 9 (1/2)(base)(height...
May 17, 2016

MATH
of course! you must have the same units 12/9 would be a meaningless calculation. 36 ft ÷ (9/12) ft = 48 Now, the question is not clear about posts at the end. e.g. If the fence has one side along a house, would you need a post right against the house at each end? If so ...
May 17, 2016

math
term5 = a+4d term2 = a+d a+4d = 2(a+d) a+4d = 2a + 2d a = 2d sum(20) = 10(2a + 19d) = 1150 2a + 19d = 115 4d+19d=115 23d = 115 d = 5 a = 10 you MUST know how to do this simple kind of question. Repeat the solution on your own, without looking at mine. Practise, practise, ...
May 17, 2016

math
volume of well = π r^2 h = π(7^2)(20) = 98π m^3 surface area to be covered by dirt = 100(42) - π(7^2) =4200 - 49π m^2 let the depth of the dirt be h m (4200 - 49π)h = 98π check and do my arithmetic
May 17, 2016

Math
What is your choice ?
May 17, 2016

Math
If expressed in terms of y ... 4y = 2x y = (2/4)x = (1/2)x so yes, with k = 1/2
May 17, 2016

Math/algebra
- find the mean - take the difference between each of your data values and the mean - square each of these differences - add up these squares of differences - divide by 10 - take the square root I will not do the arithmetic of that for you
May 17, 2016

Math/algebra
you have a GP, with a = -2, r = -2 term(20) = a r^19 = -2(-2)^19 = (-2)^20 = 2^20 = 1,048,576
May 17, 2016

Math Help Please I Don't Understand
you have to be familiar with the meaning of the constants in an equation such as y = a sin k(Ø+d) + c a is the amplitude, our range of heights is 60 ft so a = 30 y = 30sin kt + c , where t is in minutes the lowest value so far would be -30, but we need our lowest to be...
May 17, 2016

Geometry
So you want them to be an arithmetic sequence 19 , 19+d, 19+2d, 19+3d but 19+3d = 55 3d= 36 d = 12 etc
May 17, 2016

MATH
Let the width be w area of first = 12w area of 2nd = 8w 12w - 8w = 320 carry on
May 17, 2016

math
I noticed that Steve answered this for you 20 minutes ago. Why are you repeating it ?
May 17, 2016

Algebra
The way you typed it, it would be undefined for x = 0 if you meant: (x+1)(x-2)/(x^2-25) then it would be undefined for x = ± 5
May 16, 2016

Algebra
so your height formula is h = -4.9t^2 + 4.9t + 0 , assuming kicked from ground when it lands, h = 0 -4.9t^2 + 4.9t = 0 -4.9t(t - 1) = 0 t = 0 ----> at the moment the ball is kicked or t = 1, it lands 1 second later
May 16, 2016

Finance
This is a normal amount of annuity problem payment = 650 i = .078/4 = .0195 n = 4(5) = 20 amount = 650 ( 1.0195^20 - 1)/.0195 = $15,714.90
May 16, 2016

math
you will be in the 4th quadrant, 39° down from the x-axis cos 39° = x/800 x = 800cos39 = 621.7 m east y = 800sin39 = 503.5 m south notice : 621.7^2 + 503.5^2 = 639979.1489 √639979.1489 = 799.987 , not bad
May 16, 2016

Math
y^2 + 9y + 9 = 0 straightforward quadratic equation, unfortunately it does not factor, so .... by the formula y = (-9 ± √45)/2
May 16, 2016

Math(Reiny Could You Help?)
the vertex of f(x) is (2,9) The vertex of g(x) is to the right 2 units and 5 units down, so its vertex must be (4,4) since the "shape" has to be the same, we need the same 3 in front so g(x) = 3(x-4)^2 + 4 domain: the set of real numbers range: y ≥ 4 , since ...
May 16, 2016

Math
golf balls ---- 20x tennis balls -- 5x 20x+5x = 100 25x = 100 x = 4 so 80 golf balls and 20 tennis balls
May 16, 2016

Geometry
slope of AB = (4+8)/(-9+7) = 12/-2 = -6 so the slope of the perpendicular = 1/6 midpoint of AB = (-8,-2) equation of our line: y + 2 = (1/6)(x+8) 6y + 12 = x+8 x - 6y = 4
May 16, 2016

math
We clearly need a diagram to know what you are talking about. Since we cannot post diagrams here, ......
May 16, 2016

Math
your function is modelled by a parabola which opens downwards. when the package reaches the water, h(t) = 0 -4.9t^2 + 10t + 1200 = 0 t = (-10 ± √23620)/-9.8 = -14.662 or 16.7029 We will reject the negative time, so it took appr 16.7 seconds for the package to ...
May 16, 2016

Math (Trig)
you know that the point is in quad II and tanØ = 2/-1 I know that for tanØ= +2, Ø = appr 1.107 so our angle in II is Ø = π-1.107 = 2.0344 so it has to be (5, 2.0344) if you use the form (r,Ø)
May 16, 2016

Math
I don't like the wording "repeatedly" Usually this type of question uses "continuously" to describe the increase. amount = a e^(kt) , where k is the annual rate , t is the time in years and a is the initial amount. e^(k(9.25)) = 2 take ln of both sides ...
May 16, 2016

math
A not-so-subtle way to promote two wineries??
May 16, 2016

Calculus
We need their intersection: 2x^2 - 2 = x^2 + 1 x^2 = 3 x = ± √3 we want only the part in the first quadrant effective height = x^2 + 1 - (2x^2 - 2) = 3 - x^2 area = ∫(3 - x^2) dx from 0 to √3 = [3x - (1/3)x^3] from 0 to √3 = 3√3 - (1/3)(3&#...
May 16, 2016

Math
h(t) = -4sin (π/4)(t-1)+2.5 The period of this function is 2π/(π/4) = 8 So we want to see where the sine curve falls below the x-axis for 3 periods of the curve, starting at t=0 0 = -4sin (π/4)(t-1)+2.5 4sin (π/4)(t-1) = 2.5 sin (π/4)(t-1) = .625 ...
May 16, 2016

math
f+k = 1548 f+j = 1842 subtract those two equations: j-k = 294 j = 294 + k k/j = 4/7 4j = 7k j = 7k/4 sub into j = 294+k 7k/4 = 294 + k times 4 7k = 1176 + 4k 3k=1176 k = 392 then j = (7/4)(392) = 686 f+j = 1842 f = 1156
May 16, 2016

math
227.5( 1- (1+i)^-60)/i = 9500 You will need some "fancy" methods to solve this type of an equation, e.g. Newton's Method I just ran it through Wolfram and got i = .0127495 for a monthly rate or an annual rate of appr . .152994 or appr 15.3% per annum compounded ...
May 16, 2016

Statistics
I assumed you know how to find the mean and sd for the given information.
May 15, 2016

Statistics
straightforward .... find z scores for both 12 and 14 minutes go to the chart, look up the two z-scores proabilities, then subtract them
May 15, 2016

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