Sunday

October 4, 2015
Total # Posts: 31,177

**calculus**

I used to cut open a paper drinking cup in class when I was teaching this particular question. It was easy to see that the resulting arc was equal to the circular base of the cup and the "slant" height of the cup was the radius of the partial circle. Try this, and ...
*April 8, 2015*

**Math**

Would 4 x 1/7 equal 8/7 ?? Are you just guessing?
*April 8, 2015*

**Math**

The way your typed it, I do not understand the question.
*April 8, 2015*

**Math**

And what is the common factor of 3x and of 12 ??
*April 8, 2015*

**Math didn't post problem right**

I noticed you changed your divisor from 12 to 21 Don't you have a calculator ? Even an approximation of 1800/20 = 90 would have given you a clue about the right answer.
*April 8, 2015*

**Math**

Prob(5) = 1/6 prob(blue) = 1/4 what is (1/6)(1/4) ??
*April 8, 2015*

**Math**

Just checked by first calculation, should have been 72√3/2 or appr 62.4 My conclusion remains the same
*April 8, 2015*

**Math**

yes, they can case 1 : a triangular prism with an equilateral base of 12 cm per side, and a height of 10 cm volume = area of base x height = (1/2)(12)(12)sin60 = 72√3 or appr 124.7 cm^3 Notice the perimeter of the base is 36 and the height is 10 case 2: a rectangular ...
*April 8, 2015*

**Math**

You don't say if the sun is showing on its forward or its backwards leaning side. One triangle would have sides of 55.9m 90 m and an angle of 84.5° between simple application of the cosine law to find the distance between the end of the shadow and the top of the tower...
*April 8, 2015*

**Math 141**

two ways to get a sum of 3 either 12 or 21 our possible outcomes, sum ≤ 6 : 11, 12, 13, 14, 15 21, 22, 23, 24 31,32, 33, 41, 42 51 15 of them prob(your event) = 2/15
*April 8, 2015*

**PRE - CALCULUS**

type powers this way: (2x+5)^2 = 49 so 2x+5 = ±7 2x = 2 or 2x = -12 x = 1 or x = -6
*April 8, 2015*

**PRE - CALCULUS**

If you mean 3√((-4)^3) then = 2√-64 , which is not a real number
*April 8, 2015*

**exponential equations**

come on, this is the same as all the others of this type that you posted. What is your solution for this question?
*April 8, 2015*

**exponential equations**

400(2)^(72/d) = 6400 2^(72/d = 16 = 2^4 so 72/d = 4 4d = 72 d = 18
*April 8, 2015*

**exponential equations**

We did this for you this morning Why are you reposting it? http://www.jiskha.com/display.cgi?id=1428502111
*April 8, 2015*

**Finite Math**

let the rate be i 24000(1+i)^5 = 34616 (1+i)^5 = 1.44233.. take the 5th root of both sides to get 1+i = ..... isolate i and you are done
*April 8, 2015*

**math**

huh? isn't area = length x width ? so area = 8(6x+3) = 48x + 24 Trying to figure out how you could possibly come up with 9x+8
*April 8, 2015*

**MATH**

Find the perimeter in yards : use 2L + 2W change that to feet by multiplying by 3 Divide by 10 to get the number of gallons
*April 8, 2015*

**Exponential Equations**

You might want the equation: number = 1000 (2^(t/18) ) so when t = 180 number = 1000 (2^10) = 1000(2^10) , the same result that Damon got
*April 8, 2015*

**algebra**

You can generate a Pythagorean triple using the following "formula" take any values of m and n, where m > n then 2mn m^2 - n^2 m^2 + n^2 will form a Pythagorean triple e.g. m = 6 , n = 5 2mn = 60 m^2-n^2 = 11 m^2 + n^2 = 61 and 60^2 + 11^2 = 61^2 so 11, 60, 61 ...
*April 8, 2015*

**math help**

6^x 2-3^x.2^x 1/6^x-1 I will assume it is something like (6^x)^2 - (3^x)(2^x) ?? 1/( (6^x)^-1 = (6^x)^2 - 6^x ?? 6^x can't make out the last part (where I have ??), missing an operator like + or - or ..
*April 7, 2015*

**Algebra**

let y = 5^(3/4) then your expression becomes ( (5x)^(3/4) )^2 + 2(5^(3/4) + 1 = y^2 + 2y + 1 = (y + 1)^2 = ( 5x^(3/4) + 1)^2
*April 7, 2015*

**math**

i = .08/4 = .02 ----- because of "compounded quarterly" n = 5(4) = 20 ----- there are 20 quarters. plug into "amount of annuity" formula
*April 7, 2015*

**Business math**

careful, the payments are made at the beginning of each period, where the formulas we use assume that payments are made at the end of the period i = .12/2 = .06 n = 8(2) = 16 but we will use only 15 and I will assume that the first payment is $1200 is made NOW. PV = 1200 + ...
*April 7, 2015*

**Algebra**

This is just a "homework dump". Now, with which particular question did you run into difficulties? Show me the steps you took leading up to your difficulty. Btw, the cut-and-paste clearly did not work for the last two questions.
*April 7, 2015*

**Math**

distance now = 8.5 one week from now = 8.5(1.15) two weeks from now = 8.5(1.15)^2 = 11.24
*April 7, 2015*

**Exponential Equations**

1000(1+r)^2 = 1175 (1+r)^2 = 1.175 take √ of both sides 1+r = 1.08397.. r = appr .0840 or 8.40%
*April 7, 2015*

**algebra**

determinant of coefficient matrix 1 3 2 2 -1 -3 5 2 1 is -28 now replace the first column with the the constants coefficients 3 3 2 -8 -1 -3 9 2 1 and the determinant of that is -56 do a = -56/-28 = 2 now replace the 2nd column with the constants and find the determinant to ...
*April 7, 2015*

**math**

So the total score for all 100 students is 7710 Two more students added 125 for a new total of 7835 new average = 7835/102 = 76.8 2. total = 12 bb-players + 18 baseball players = 30 players but there were only 24 , so 6 must have been playing both sports. check: 12+18-6 = 24
*April 7, 2015*

**Calculus**

just notice I skipped the -2x term so our derivative should be . 2(2)dy/dt + 2(-1)(-4) - 2dx/dt + 6(-1)^2 dy/dt = 0 2(2)dy/dt + 2(-1)(-4) - 2(-4) + 6(-1)^2 dy/dt = 0 4dy/dt + 8 + 8 + 6dy/dt = 0 dy/dt = -16/10 = -1.6
*April 6, 2015*

**Calculus**

your 2(2)dy/dt+(2)(-1)(-4)+6(-1)^2=0 should have been 2(2)dy/dt + 2(-1)(-4) + 6(-1)^2 dy/dt = 0 4 dy/dt + 8 + 6dy/dt = 0 10dy/dt = -8 dy/dt = -4/5 I don't see any errors.
*April 6, 2015*

**Calculus**

use implicit derivatives .... 2x dy/dt + 2y dx/dt + 6y^2 dy/dt = 0 now just plug in the given stuff.
*April 6, 2015*

**Calculus**

Profit(x) = R(x) - C(x) = 60x - .5x^2 - 5x - 15 = -.5x^2 + 55x - 15 dPdt (x) = -x dx/dt+ 55 = -30(20) + 55 = .....
*April 6, 2015*

**Calculus**

same as your other question. check your work, that should have been √171 instead of √192 25 + y^2 = 14^2 y^2 = 196 - 25 etc
*April 6, 2015*

**intermediate algebra**

3/((x+3)(x-3))- x/(x-3)(x-3) + 1/(x+3) The LCD is (x-3)(x-3)(x+3) = (3(x-3) - x(x+3) + 1/((x-3)(x-3))/((x-3)(x-3)(x+3)) = .... take over
*April 6, 2015*

**Calculus**

you are right, I got my fraction upside down, sorry dy/dx = -2/√140 = appr -.169
*April 6, 2015*

**Calculus**

This is the classic example used by most textbooks in the introduction to Related Rates in Calculus. let the foot of the ladder be x ft from the wall, let the ladder reach y ft above the ground x^2 + y^2 = 12^2 2x dx/dt + 2y dy/dt = 0 or x dx/dt + y dy/dt = 0 given: dx/dt = 1 ...
*April 6, 2015*

**math please help**

done, check back to earlier post and correction
*April 6, 2015*

**Math**

I would make a sketch of each function on the same grid. Also they told you what to do in the hint, why not do that?
*April 6, 2015*

**Math**

Check for the solution and the correction I just made to your previous post
*April 6, 2015*

**Pre-Calculus**

I agree with you x^2+9x+20 = x^2 + 9x + 81/4 - 81/4 + 20 = (x+9/2) + 20 - 81/4 = (x+9/2)^ - 1/4
*April 6, 2015*

**correction - math**

I misread your c = 5.5 as c = 3.5 , sorry about that So AD should be 2.75 But AC is still greater than 2.75 so no real harm done, all you have to do is change the 3.5 to 5.5 and use the new values. The conclusion is still the same, but make sure you get the new angles.
*April 6, 2015*

**math**

First let's see if it is possible. Start with a base of BC, sketch an angle of 30° at B and draw a line BA = 3.5 sketch in an altitude from A to BC to meet BC at D sin30° = AD/3.5 AD = 3.5(1/2) = 1.75 Since AC > 1.75, it will be possible to draw the triangle. As...
*April 6, 2015*

**AP CALC**

then y = c e^(kt) when t = 4 4c = c e^(4k) 4 = e^ 4k 4k = ln4 k = ln4/4 y = 1500 e^((ln4/4)t) so when t = 3 y = 1500 (e^(3ln4/4) = appr 4243 check: at t=4 y = 1500 e^(4ln4/4) = 6000
*April 6, 2015*

**geometry**

let C be (a,b) by the midpoint theorem we know: (-3+a)/2 = 5 and (2 + b)/2 = -4 -3+a = 10 and 2+b = -8 a = 13 and b = -10 so A is (-3,2) , C is (13,-10), and the midpoint between them is B(5,-4) You should have seen that your answer is incorrect as soon as you graphed it. (I ...
*April 6, 2015*

**Algebra**

You probably do not recognize that as a "sum of cubles" facoring result, if you do, you can jump directly to the final line, otherwise .... So let y = 5x^(1/3) , then 25x^(2/3) can be written as (5x^(1/3))^2 = y^2 so we have (y + 1)(y^2 - y + 1) = y^3 + 1 = (5x^(1/3...
*April 6, 2015*

**Math**

the official radius of a ping pong ball is 20 mm or 2 cm so the volume of a ball is (4/3)π(2^3) = appr 33.5 cm^3. which Ms Sue has correctly as 2.045 inches^3 but the balls will not "stack" nicely. Did you ever look at a stack of cannonballs at some fort? If we ...
*April 6, 2015*

**Math**

volumes of similar solids are proportional to the cube of their sides so volume of original = 8m^3 volume of new is 72 m^3 so let's take the smallest dimension of 1 m , since it is a unit dimension. 8/72 = 1^3/x^3 8x^3 = 72 x^3 = 9^(1/3) x = 9^(1/3) = appr 2.08 So, he ...
*April 6, 2015*

**Algebra**

= t + 4t^(1/2) + 4 or = t + 4√t + 4
*April 6, 2015*

**math**

You haven't even defined any variables, so what equations did you get?
*April 6, 2015*

**Finite Math**

treat P(R and S) as a variable, suppose it is x, then your first equation becomes P(R or S) = P(R) + P(S) - x , .... you have a typo here .64 = .38 + .52 - x x = .9 - .64 x = .26 P(R and S) = .26
*April 6, 2015*

**Math Check**

Did you even look at my reply to your same question which you posted less than 1 hour ago ? http://www.jiskha.com/display.cgi?id=1428346534
*April 6, 2015*

**Math Help Please!**

Without even doing any calculation, since there is such a large difference in the interest rates, it should be obvious that the simple interest plan should be the better of the two. check: at simple interest I = 2000(.13)(4) = 1040 so amount in your account = 3040 at compound ...
*April 6, 2015*

**math**

look at my concern about this problem in your earlier post
*April 6, 2015*

**Math: Geometry**

a) the block was (15)(8)(5) cm^3 = ..... you have to know the volume of a cylinder , which is v = π r^2 h You don't say in which direction the holes are drilled, so I can't continue
*April 6, 2015*

**Math**

If this relation were to be even remotely true, we could form a ratio .... 18 months/36 inches = 60 months/x inches 18x = 2160 x = 120 inches or 10 ft tall (can you see how absurd your question is ???? ) Also in h = 2c , you don't define what h and c stand for.
*April 6, 2015*

**algebra**

first step: (a^3 - b^3)(a^3 + b^3) second step: we can factor the sum and difference of cubes, should be in your notes or text = (a-b)(a^2 + ab + b^2)(a+b)(a^2 - ab + b^2)
*April 6, 2015*

**maths**

That is, 8x - 163 = 3x -13
*April 6, 2015*

**math**

mmmmhhh , been on this earth over 75 years, and guess what, each of those years had 4 seasons (4 quarters) , so 4 years will have 16 quarters. notice that the interest rate is compounded quarterly, so we need the rate per quarter. That is i = .06/4 = .015 n = 16 I have no clue...
*April 6, 2015*

**math**

i = .06/4 = .015 n= 4(4) = 16 Present value of payment option = 2400(1 - 1.015)^-16)/.015 = 33915.03 Well, what do you think ?
*April 6, 2015*

**math**

Prob(green, then yellow) = (5/30)(8/29) = 4/87
*April 6, 2015*

**Math**

-8x^2-8x-2=0 or 4x^2 + 4x + 1 = 0 discrm = 16 - 4(4)(1) = 0 thus there is one solution. check: 4x^2 + 4x + 1 = 0 (2x + 1)^2 = 0 2x+1 = 0 x = -1/2
*April 6, 2015*

**Precal**

change 9 to base 3 as 9 = 3^2 (3^2)^x^2 = 3^(-5x - 2) so : 2x^2 = -5x-2 2x^2 + 5x + 2= 0 (2x + 1)(x + 2) = 0 x = -1/2 or x = -2
*April 5, 2015*

**calc 1**

Look at the solution I gave Ryan for an almost identical problem as yours http://www.jiskha.com/display.cgi?id=1427010949
*April 5, 2015*

**Math**

I think Steve is missing part of the formula and/or using the wrong formula. PV = paym(1 - (1+i)^-n)/i so here PV = 900(1 - 1.02^-16)/.02 = $12,219.94 So he should take the payment option.
*April 5, 2015*

**algebra**

I will read that as: (x+3)/x^3 ÷ 6/(x-3) then ... = (x+3)/x^3 * (x-3)/6 = (x^2 - 9)/(6x^3)
*April 5, 2015*

**math**

You don't tell me what your x represents, but from your equation I conclude that you defined x to be each of the 3 parallel sides and y as the length of the whole field then area = xy = x(2250 - 1.5x) = -1.5x^2 + 2250x your A(x) = 2250 - 1.5x^2 is almost correct, but it is...
*April 4, 2015*

**math**

divide your equation by 50 20x + 10y + z = 200 remember that x, y, and z must be positive whole numbers. Are we allowed to have zero of any of them ???? I will let you decide that z = 200 - 20x - 10y maximum value of x has to be 9, (if x=10, z = 0) maximum value of y has to be...
*April 4, 2015*

**algebra**

One small change from your previous problem. Instead of 46 minutes you now have 54 minutes.
*April 4, 2015*

**algebra**

distance outside city --- x distance inside city ---- 33-x time = distance/rate x/50 + (33-x)/30 = 46/60 solve for x (I suggest multiplying each of the 3 terms by 300)
*April 4, 2015*

**math**

points depend on the number of prizes
*April 4, 2015*

**Trigonometry**

first answer line should be 1. y = 2 sin 4(x - π/8) + 1 or y = 2 sin (4x - π/2) + 1
*April 4, 2015*

**disagree - rigonometry**

I disagree with your phase shift in general: y = a sin k(x - d) + c the phase shift is d. Notice that the period indicator k is factored out In your answer we have ... sin(4x - π/8) ... or ... sin 4(x - π/32)... So the phase shift of your equation would be π/32 ...
*April 4, 2015*

**maths**

circumference = 40π cm so in one minute would cover 50(40π) or 2000π cm to cover 6.28 km or 628000 cm would take 628000/(2000π) minutes , or 99.949.... minutes, which is appr 1hr and 40 minutes
*April 4, 2015*

**geometry**

let the third side be x , where x is a positive number FACT: the sum of any two sides of a triangle must be greater than the third side, so 22+34 > x AND 22+x > 34 AND 34+x > 22 clearly 34+x is always > 22, so for the other two ... 56 > x AND x > 12 or 12 <...
*April 3, 2015*

**geometry**

Don't all three angles add up to 180° ? Use this fact to form your equation, then solve it
*April 3, 2015*

**math discrete 2**

Since it is linear, we can just "reverse" our steps. e.g. for g(x) , for any x, the first thing we do is multiply it by 4 and then subtract 5 now doing this backwards, start with an x, add 5, then divide that be 4 so g^-1 (x) = (x+5)/4 standard method: step1 : ...
*April 3, 2015*

**math discrete**

h◦(g◦f) = h(g(f(x) ) ) = h(g(4x^3 - 5) ) ) = h(2(4x^3 - 5)) = ( 2(4x^3 - 5) )^2 manipulate this if needed. testing with some value, say x = 2 according to my result: (2(32-5))^2 = 2916 long way: f(2) = 27 g(27) = 54 h(54) = 2916
*April 3, 2015*

**Math**

Did you make your sketch?? According to mine it is a simple case of the cosine law HB^2 = 270^2 + 160^2 - 2(270)(160)cos 23° = .. take over
*April 3, 2015*

**Math - Help Me Please**

cost = 300 + 40(1 - 1.0325^-24)/.0325 = $ 959.53 interest paid = 300 + 24(40) - 959.53 = $300.47 Wow, that is 39% . Is that even legal? In the middle ages they would have burned you at the stake for usury.
*April 3, 2015*

**pre calculus**

cost = 2000 + 15(x-100) , x ≥ 100 b) just divide all of the above by x c) plug in your x d) set your equation in a) equal to 16
*April 3, 2015*

**present value**

PV = 20000(1.04)^-1 + 10000(1.04^-2 + 1.04^-3 + 1.04^-4 + 1.04^-5) = ... you push the buttons
*April 3, 2015*

**Geometry help**

original: length --- x width ---- y height ---z xyz = 420 new prism length --- x/2 width ---- y/3 height --- z (x/2)(y/3)z = = xyz/6 = 420/6 = 70 units3 notice it wouldn't matter which dimensions are halved and cut into thirds, I could have used other combinations. The ...
*April 3, 2015*

**math**

That would be an example. To solve it, I would change the 2nd to y = 24-4x and sub that into the 1st.
*April 3, 2015*

**Algebra**

Were the "givings" consecutive or simultaneous ?
*April 3, 2015*

**math**

Present Value = 900(1 - 1.0041666..)^-300)/.0041666... = $153,954.05
*April 3, 2015*

**M ath**

i = .09/12 = .0075 a) n = 9(12 = 108 pmt( 1 - 1.0075^-108)/.0075 = 26000 pmt = $352.12 b) I will assume you know what changes to make for b)
*April 3, 2015*

**Math/Calculus**

I agree
*April 2, 2015*

**math- please help me - Ms. Sue**

The above method results in an interest rate much higher than 18%. Explanation: The $216 of simple interest would be valid if there were no payments made and you would just pay back the $816 after 2 years. BUT, you are making payments of $34 each month so the balance keeps ...
*April 2, 2015*

**Math**

you are correct.
*April 2, 2015*

**Algebra help Will only take a minute**

Plug in n = 1 , 2, 3, 4 , .... and see what you get remember, you have to calculate the power before you multiply by 5
*April 2, 2015*

**Math please help**

I got the same results, and I stand by them
*April 2, 2015*

**Math please help**

Every angle can be found. In triangle CAT, use the sine law to find AC and in triangle BAT, use the sine law to find AB Area of triangle ABC = (1/2)(AC)(AB)sin 60° = ...
*April 2, 2015*

**math please help**

mmmh, and we are supposed to guess where ?
*April 2, 2015*

**math please help**

Where do points D and E enter the picture ?
*April 2, 2015*

**Math, Science**

h = -4.9t^2 + 15t take derivative, set equal to zero, and solve for t plug t back into h = ...
*April 2, 2015*

**calculus**

A litter is a group of kittens, a litre is a fluid measure of 1000 ml let the height be h cm let the radius be r cm πr^2 h = 200 h = 200/(πr^2) amount of material ---> surface area (SA) SA = 2πr^2 + 2πrh = 2πr^2 + 2πr(200/(πr^2)) = 2π...
*April 2, 2015*

**Algebra**

The instructions appear quite clear, where does your problem arise? I will do a) Left Side = g(x+2) = 7(x+2) - 2 = 7x + 14 - 2 = 7x + 12 Right Side = g(x) + g(2) = 7x - 2 + 12 - 2 = 7x +8 Thus g(x+2) ≠ g(x) + g(2) do the others in a similar way
*April 2, 2015*

**algebra**

The speed of the wind is indeed 200/7 or 28.57 mph check: with the help of the wind the plane is moving at 228.57 mph, for 6 hrs = 1371.43 kkm against the wind, the plane is moving at 200-28.57 or 171.43 km/h, and for 6 hours that would be 1028.57 and (3/4)(1371.43) = 1028.57 ...
*April 2, 2015*

**algebra**

let the speed of the wind be x km/h so distance with the wind = 6(200+x) km distance against the wind = 6(200-x) but 6(200-x) = (3/4)(6(200+x)) solve for x , let me know what you get.
*April 2, 2015*