Wednesday

June 29, 2016
Total # Posts: 35,092

**Calculus**

Wow, nice problem with very clear and precise instructions how to do it. I suggest you just follow the steps they ask you to perform. I will start you off. Let the finished box be x inches long, y inches wide and 3 inches high given: 3xy = 2760 xy = 920 original piece is (x+6...
*June 13, 2016*

**math**

cone = (1/3)π r^2 h where r = 1.5 h = 12 find the volume of the cone, just plug in the values Can = π r^2 h r = 2 h = 2 volume of can = ..... compare to see which is larger. take the difference to see which hold more
*June 13, 2016*

**Math**

Let AC = x let AB = 2x We can use the cosine law to find x x^2 + (2x)^2 - 2(x)(2x)cos120° = 8^2 5x^2 - 4x^2(-1/2) = 64 7x^2 = 64 x^2 = 64/7 x = 8/√7 perimeter = x+2x+8 = 3x + 8 = 24/√7 + 8 = appr 17
*June 13, 2016*

**Algebra**

I think they want the equation in the form ax^2 + bx + c = 0, where a is a positive real number so just "move" all the terms to the left side and set them equal to zero e.g. #5 4x + 3 = x^2 -x^2 + 4x + 3 = 0 x^2 - 4z - 3 = 0 Do the others the same way, it is really ...
*June 11, 2016*

**College Algebra II**

The midpoint of (a,b) and (c,d) is ( (a+c)/2 , (b+d)/2) ) let P2 be (c,d) for the x value : (c + (-2) )/2 = -1 c -2 = -2 c = 0 find the y value of P2 in the same way. Check by finding the midpoint of P1 and P2 using the formula I gave, and make sure you get the point (-1,3)
*June 11, 2016*

**Math**

A = {2,3,5} and B = {1, 3, 5} 2+1 = 2+3 = 2 + 5 = 3+1 = 3+3 = 3+5 = 5+1 = 5+3 = already have that 5+5 = make sure you don't count equal sums twice, e.g. 3+3 = 6 5+1 = 6 You are just looking at the different sums
*June 11, 2016*

**Math**

no in a phase shift, the shape of the sine curve does not change, but in a period change you are changing the shape
*June 11, 2016*

**Math**

Did you mean that 3 of the angles are in the ratio of 2:3:7 ? let those three angles be 2x, 3x, and 7x let the fourth angle be y 2x + 3x + 7x + y = 360 y + 12x = 360 y = 360 - 12x "the mean of these angles is 64" I will assume you mean the mean of the 3 angles. 12x/3...
*June 11, 2016*

**Math**

x^2 + 13x - 30 = 0 (x-2)(x+15) = 0 x = 2 or x = -15 which is the smaller ?
*June 11, 2016*

**Math**

original fraction: x/(x+4) new fraction = (x+3)/(x+7) (x+3)/(x+7) = 3/4 4(x+3) = 3(x+7) solve for x, and sub back into original fraction
*June 11, 2016*

**math**

ummmh, so the sum is 18 made of 6 equal digits?? What do you think?
*June 11, 2016*

**algebra**

Just stating the answer is not helping Tourille learning how to do this.
*June 11, 2016*

**Calculus**

Let one of them be x, and the other one y xy = 2 y = 2/x sum = x+y = x + 2/x d(sum)/dx = 1 - 2/x^2 = 0 for a min sum 1 = 2/x^2 x^2 = 2 x = √2 , then y = 2/√2 = √2 their minimum sum = x+y = √2 + √2 = 2√2
*June 10, 2016*

**Math**

tried to find a relation, could not find a definite one. the graph looks almost linear. http://www.wolframalpha.com/input/?i=pattern(100,+105,107,110,+115,120,123,126) (I used units of 1000) What is your depth of study of this? Have you learned about "equations or lines ...
*June 10, 2016*

**Math**

What are we finding? The equation? let y = kx for the given values: 3 = 7k k = 3/7 so y = (3/7)x or x = (7/3)y or y/x = 3/7 or y : x = 3 : 7 etc
*June 10, 2016*

**Algebra 1**

slope = (y2 - y1)/(x2 - x1) = (2-4)/(3-(-4) ) = .....
*June 10, 2016*

**Math (pre-celc 12)**

since you labelled this "pre-calculus" , I suppose we can't use the derivative, which would be the easiest way of doing it consider: y = 6 cos( (2π/14)x) the period = 2π/(2π/14) = 14 You had that. so we have a cosine curve with a max of 6 when x = ...
*June 10, 2016*

**Algebra**

You know that the equation in the form y = mx + b has to be y = (7/3)x + b plug in the given point: 11 = (7/3)(3) + b 11 = 7 + b b = 4 y = (7/3)x + 4
*June 9, 2016*

**MATH**

Thank you Ms Sue.
*June 9, 2016*

**MATH**

You sure got me on that "were" vs "where". As to education vs dancing, you are absolutely free to set your priorities.
*June 9, 2016*

**Dear Mom - MATH**

Sorry to say this, but if you are homeschooling your child and you are "completely lost" with this routine question, perhaps it is time to send him/her to a regular school were qualified math teachers can do it. both Steve and I have both answered this question, ...
*June 9, 2016*

**ALGEBRAA**

I have seen this same question about 4 times now Steve just answered it for you here: http://www.jiskha.com/display.cgi?id=1465520203 You even thanked him. Why are you repeating it ?
*June 9, 2016*

**Math**

why are you switching names? http://www.jiskha.com/display.cgi?id=1465510795
*June 9, 2016*

**math**

suppose we have f(x) = 3x^3 - 5x^2 + 4x + 1 and we divide that by x-2 ( I can't show the long algebraic division in this format, but I am sure you know how to do that) you should have 3x^2 + x + 6 with a remainder of 13 now let's find f(2) f(2) = 3(8) - 5(4) + 4(2) + 1...
*June 9, 2016*

**math**

What have you got so far for this assignment? You didn't expect me to just do it for you, did you?
*June 9, 2016*

**algebra**

Did you mean it the way you typed it, then by the order of operations.... x + 1x= b/x, since a/a = 1 2x = b/x 2x^2 = b x^2 = √(b/2) for extraneous roots, a can be any non-zero number, and b < 0 If you meant: (x+a)/(ax) = b/x x^2 + ax = abx x^2 + ax - abx = 0 x^2 + x(a...
*June 9, 2016*

**ALGEBRA**

Do you have a programmable calculator such as TI which does graphs? How do you expect me to do this for you ? There are all kinds of suitable webpages that will do graphs for you. This one is one of the best: http://www.wolframalpha.com/input/?i=plot+y+%3D+(3x+-+4)%2F(x+%2B+2...
*June 9, 2016*

**ALGEBRA**

how about y = (3x - 4)/(x + 2)
*June 9, 2016*

**Math(Please Help Assignment Due)**

look back when you first posted this
*June 9, 2016*

**Parametric Equations**

I would have chosen that one too
*June 9, 2016*

**Algebra**

ummmhhh, yes
*June 9, 2016*

**Algebra**

y = x^2 + 3x + 5 y = x + 13 solution: x^2 + 3x + 5 = x + 13 x^2 + 2x -8 = 0 (x+4)(x-2) = 0 x = -4 or x = 2 if x = -4, y = 9 if x = 2 , y = 15 http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E2+%2B+3x+%2B+5,+y+%3D+x+%2B+13
*June 9, 2016*

**Math2**

-think of a number ----- x - triple it -------------- 3x - add 6 ---------------3x+6 - divide by 3 ---------x+2 - add 5 -------------- x+7 - subtract your original number -------- 7 Paula now knows the number Jessica ended up with. always 7 !
*June 9, 2016*

**Math**

First of all, where does the first line come from? if it is true, then 7(a+b)-5(a+b)=7c-5c 2(a+b) = 2c a+b = c a+b-c = 0 so in your second last line you divided by zero, which is a mathematical No No. any subsequent conclusion you draw would be bogus.
*June 9, 2016*

**Logic and Reasoning**

You have to have brackets for your conjecture to be true 15/20 = 3/4 , then (15-3)/(20-4) = 12/16 = 3/4 18/15 = 6/5, then (18-6)/(15-5) = 12/10 = 6/5 suppose a fraction a/b is not in lowest terms and can be reduced to c/d then a/b = c/d = k is (a-c)/(b-d) = k ?? from c/d = k, ...
*June 9, 2016*

**trigonometry**

ahh, the old "missing bracket" trap. Thanks Steve.
*June 8, 2016*

**trigonometry**

I will write it as: (cosx + cosy)² + (sinx + siny)² = 4cot(x-y/2) --> easier to type LS = cos^2 x + 2cosxcosy + cos^2 y + sin^2 x + 2sinxsiny + sin^2 x = sin^2 x + cos^2 x + sin^ y + cos^2 y + 2(cosxcosy + sinxsiny) = 2 + 2cos(x - y) = 2(1 + cos(x-y) ) RS = 4 cot(...
*June 8, 2016*

**Math**

You should know that the volume of a cone = (1/3)π r^2 h Just plug in your data
*June 8, 2016*

**Math**

No algebra or variables needed here. Just do the arithmetic. "Harry has $120. Harry has 3 times as much money as Tom" ---> so Tom has $40 "Tom has twice as much money as Gabi" ----> Gabi has $20
*June 8, 2016*

**statistics**

z-score = ( X - mean)/sd z-score = (95-80)/10 = 1.5
*June 8, 2016*

**Math**

The last part of the sentence " if it is known that tails occurs at least twice?" contradicts the first part. ignoring that last part we would have: C(4,3)(1/2)^3 (1/2) = 4 (1/16) = 1/4
*June 8, 2016*

**Trigonometry**

Did you make your sketch? You have a triangle with all sides known, a clear case of the cosine law, let the angle between them be Ø 189^2 = 244^2 + 168^2 - 2(244)(168)cosØ 2(244)(168)cosØ = 244^2 + 168^2 - 189^2 cosØ = (244^2 + 168^2 - 189^2)/(2(244...
*June 8, 2016*

**math**

let n be the number he originally bought cost = 20(n/50) = 2n/5 number he sold = n-30 return = 1.2(n-30) profit equation: 1.2(n-30) - 2n/5 = 84 1.2n - 36 - 2n/5 = 84 1.2n - .4n = 120 .8n = 120 n = 150 he bought 150 tomatoes check: cost to buy them = 20(150/50) = $60 return = 1...
*June 8, 2016*

**Math**

3n - 12 = 30 3n = 42 n = 42/3 or 14 years
*June 8, 2016*

**Math**

no, look at how "an apple is 10% lighter ..." became .9 so what percentage do I need to have .8333... ?
*June 8, 2016*

**Math**

g = 1.08 o -----> o = g/1.08 a = .9 o ---> o = a/.9 g/1.08 = a/.9 .9 g = 1.08a a = (.9/1.08) g a = .8333... g state your conclusion.
*June 8, 2016*

**Math**

What changes do you think you have to make in my solution? http://www.jiskha.com/display.cgi?id=1465418863
*June 8, 2016*

**Pre-Calculus Matrix**

never mind the matrix stuff. Suppose we subtract #3 - #1 I get x + 4y + 6z = 8 but #2 says: x + 4y + 6z = -32 which contradicts the above, so .... no solution
*June 8, 2016*

**Math**

yes
*June 8, 2016*

**Math**

how did you get that? Are we including the area of the base ?
*June 8, 2016*

**math**

if you want the eastward displacement ... x/50 = cos 10° x = .....
*June 8, 2016*

**Math**

I think you missed my point. I was pointing out that there is no octagon possible with sides of 19 and apothem of 16. Carefully read what my explanation said. Thus, none of the answers make any sense. Please let your teacher know, so he/she can correct the worksheet. Just ...
*June 8, 2016*

**Math**

There is a problem with your question. You said it was a regular octagon with sides 19 inches, forget the apothem part right now. Then you have 8 equal isosceles triangles with an angle of 360/8 or 45° at the top and angles of 67.5° at each of the bases. The height of ...
*June 8, 2016*

**Math**

in general if the centre is (h,k), the equation is (x-h)^2 + (y-k)^2 = r^2 notice that the sign inside the bracket is opposite to the sign used in the given point. so for (-4,-3) it must be (x-(-4) )^2 + (y - (-3) )^2 = r^2 (x+4)^2 + (y+3)^2 = r^2 to find the r^2, just plug in...
*June 8, 2016*

**Algebra**

Without brackets, your question and your answer is ambigious. I will assume you want cuberoot(3√540 r^3 s^2 t^9) = (3√540r^3 r^3 s^2 t^9)^(1/3) = [3√((36)(15) r^3 s^2 (t^3)^3]^(1/3) = [ 18√15 r^3 s^2 (t^3)^3]^(1/3) = (18√15)^(1/3) r s^(2/3) t^3 ...
*June 8, 2016*

**math**

What is C(8,2) x C(9,3) ?
*June 8, 2016*

**Math, Year 10, Simult. Equations**

Equations need an "equal" sign and usually consist of both x and y terms. Did you mean y = -x^2 + 3x + 4 and y = x-4 ? Make a table of values for each one. The first one is a downwards opening parabola, get about 4 or 5 points and you should see the general shape of ...
*June 8, 2016*

**Pre-Calculus**

agree with 1 1 1 -5 1 -1 3 -1 4 1 1 -2 -----> you had an extra 1 in there 1 1 1 -5 0 2 -2 -4 #1 - #2 0 3 3 -18 1 1 1 -5 0 1 -1 -2 #2 divided by 2 0 1 1 -6 #3 divided by 3 1 1 1 -5 0 1 -1 -2 0 0 -2 4 #2 - #3 1 1 1 -5 0 1 -1 -2 0 0 1 -2 from #3: z = -2 in #2: y - z = -2 y + 2...
*June 7, 2016*

**math**

h = -16t^2 + 60t + 3 at ground level , h = 0 16t^2 - 60t - 3 = 0 t = (60 ± √3792)/32 t = 3.799.. or t = a negative it will take appr 3.8 seconds to hit the ground
*June 7, 2016*

**Math (Polar to Cartesian Equation)**

in your repertoire of relations in this topic you should have: x = rcosØ and y = rsinØ, and r^2 = x^2 + y^2 then r/x = sec‚ and r/y = cscØ so let's just substitute r^2 = (4r/x)(r/y) r^2 = 4r^2 /(xy) 1 = 4/(xy) xy = 4
*June 7, 2016*

**Math**

LS ---> left side RS ---> ???
*June 7, 2016*

**Math**

LS = 1/(siny - 1) - 1/(siny + 1) using a common denominator: = (siny + 1 - (siny - 1)/( sin^2 y - 1) = 2/(-cos^2 y) = - 2 sec^2 y = RS
*June 7, 2016*

**math**

let their lengths be 3x, 4x, and 2x 3x+4x+2x = 72 solve for x, then sub back into my definitions
*June 7, 2016*

**Math**

I strongly suggest that you memorize the 1 , √3, 2 <------> 30-60-90° triangle. You will meet it again and again if you continue to study math
*June 7, 2016*

**Math**

sketch a right-angled triangle with angles 30-60-90 label the sides 1 , √3 and 2, with 1 opposite the 30°, etc so 2 --- x 3.5 -----> 7 and 1 -- x 3.5 -----> 3.5 or 7/2 and √3 -----------> 7√3/2 perimeter = 7 + 7/2 + 7√3/2 = 21/2 + (7/2)&#...
*June 7, 2016*

**Math**

quite simple really. since angle A = 90° and angle B = 45°, then the other angle is also 45°, and the triangle is isosceles, thus the other two sides are equal. let each side be x x^2 + x^2 = 17^2 2x^2 = 289 x^2 = 289/2 x = 17/√2 = 17/√2 * √2/&#...
*June 7, 2016*

**maths**

direct translation of the English to Math: x + x^2 = 1.5|x^2 - x| case1: times 2 2x + 2x^2 = 3x^2 - 3x x^2 - 5x = 0 x(x-5) = 0 x = 0 or x = 5 or case2: x+x^2 = 1.5(x-x^2) times 2 2x + 2x^2 = 3x - 3x^2 5x^2 - x = 0 x(5x-1) = 0 x = 0 or x = 1/5 so x = 0 , (the trivial case) or x...
*June 7, 2016*

**Math**

wage = 2500 + .07s , where s is sales
*June 7, 2016*

**Math**

Thank you Steve.
*June 6, 2016*

**Math**

so your debt would have grown to ... 4300(1.018)^15 = 5619.38 don't you love those "no payments for 2 years deals" ? They always forget to tell you there is still interest involved.
*June 6, 2016*

**Pre cal**

no, your equation doesn't even contain any variables. x(7000) + (x+.03)(13000) = 1190 7000x + 13000x + 390 = 1190 20000x = 800 x = .04 or 4%
*June 6, 2016*

**Math**

At point A, sketch in horizontals and verticals the angle between AC and the x-axis is 35° , (305° - 270°) So at A by alternate angles and parallel lines the angle between AC and the horizontal is 35° And AB divides the right angle at A into angles of 64°...
*June 6, 2016*

**French Check Ms. Sue**

number 9 is poorly worded The way of writing time in ascending order of day/month/year is standard in most of the world, including France, Canada, and English speaking countries, with the exception of the US.
*June 6, 2016*

**algebra**

At off peak rate: cost = .85t at peak time rate: cost = 1.2t I can't do the graphs for you, but I suggest for the first you use: (0,0) and (20, 17) to sketch the first graph, and (0,0) and (20, 24) for the second one sub t = 8 into off-peak equation and into the peak ...
*June 6, 2016*

**Algebra**

Strange to ask for an "estimate" for a solution to an equation that can be done mentally. n = -1/6 no idea what you mean by "use a table".
*June 6, 2016*

**math**

33 1/3% = 100/300 = 1/3 as a fraction or .333.... as a decimal (the 3 should be shown to be repeating) your decimal of .33 would be 33 % , not 33 1/3 % 78% of 20 = appr 80% of 20 = appr 16
*June 6, 2016*

**math**

for ii) I was thinking: prob(same gender) = Prob(both males) or prob(both female) = (2/3)^2 + (1/3)^2 = 4/9 + 1/9 = 5/9 prob(different gender) = 1 - 5/9 = 4/9 or Prob(male, female) or Prob(female, male) = (1/3)(2/3) + (2/3)(1/3) = 4/9
*June 6, 2016*

**geometry**

Check what you typed, how it came out, and if it makes sense to you.
*June 6, 2016*

**Math :(**

1. correct if you reduce it to 7/36 2. prob(2whites) = (2/9)(1/8) = 1/36 3. prob(2 purples) = (7/9)(6/8) = 7/12 so what do you think when comparing 1/36 with 7/12 ?
*June 6, 2016*

**maths**

number in lot A ---- x number in lot b ---- y (2/3)x + y = 400 times 3 2x + 3y = 1200 ** x + (4/5)y = 460 times 5 5x + 4y = 2300 *** ** times 4 : ---> 8x + 12y = 4800 *** times 3: --> 15x + 12y = 6900 subtract them: 7x = 2100 x = 300 in ** 600 + 3y = 1200 y = 200 total ...
*June 6, 2016*

**Algebra**

The way you typed it, it would become x = 2y/2 * y + 5 somehow I don't think you meant that. If you meant: x = 2y/(2y) + 5, the 2y would cancel and the statement would be false If you meant: x = 2y/(2y+5) cross-multiply ... 2xy + 5x = 2y 2xy - 2y = -5x y(2x - 2) = -5x y...
*June 6, 2016*

**Algebra**

Did you substitute each one to see ? How about the last one? for (5,2) is 2 = 5-3 ??
*June 6, 2016*

**Maths**

tanØ = 3/4 = y/x so x=4 and y=3 OR x = -4, y = -3 r^2 = x^2 + y^2 = 25 r = 5 cos^2 Ø - sin^2 Ø = (4/5)^2 - (3/5)^2 = 16/25 - 9/25 = 7/25
*June 6, 2016*

**MATHS**

Whatever "d/f coes" are, the must look like ABxxx, where x is one of the given digits. I will assume that repetition is allowed. no. of ways = (1)(10)(10)(10) = 1000
*June 6, 2016*

**algebra**

So the foot of the ladder is 10 ft from the building. and you want to reach a height of 13 ft L^2 = 13^2 + 10^2 = 269 L = √269 = appr 16.4 m Why do we have to know the fence is 9 ft high? Am I missing something?
*June 5, 2016*

**Math (Right Triangle Trig)**

Make a sketch in your notes regarding CAST It tells you in which quadrants the main trig ratios of (S)ine, (C)osine and (T)angent are positive. Of course if the cosine is positive then its reciprocal, the secant, is also positive, etc since tanØ = 5/7 = y/x x = -7 , y...
*June 5, 2016*

**Math**

let the distance be d and the first rate be t original time = d/t new rate = .8t new time = d/.8t = 1.25 d/t so the time increased by 25%
*June 5, 2016*

**@ Ritobroto - math**

Always check your answers before you post them. from my equation: x + x+9 + 3x = 89 5x = 80 x = 16 according to my definitions: first = 25 second = 16 third = 48 Is their sum equal to 89 ? , YES Do they fit the given conditions ?, YES Yours do not fit the original conditions ...
*June 5, 2016*

**math**

second --- x first ---- x+9 third ---- 3x x + x+9 + 3x = 89 carry on
*June 5, 2016*

**Algebra I**

e.g. √245 = x first guess: x = 15 245/15 = 16.33333 average with previous guess: (15+16.33333..)/2 = 15.6666.. <---- new guess 245/15.6666.. = 15.63829.. average with previous guess: (15.6666.. + 15.63829..)/2 = 15.65248... 245/15.65248 = 15.65246... average with ...
*June 5, 2016*

**Algebra 2**

let the 3 cosecutive odd numbers be x-2 , x, and x+2 3(x-2 + x + x+2) = x(x-2) - 152 9x = x^2 - 2x - 152 x^2 - 11x - 152 = 0 (x-19)(x + 8) = 0 x = 19, or x = -8 , but x is to be positive the 3 numbers are: 17, 19, and 21 check: their sum = 57 3 times their sum = 171 product of...
*June 5, 2016*

**Math**

let her sales be s .15s + 3000 ≥ 4200
*June 5, 2016*

**Algebra 2**

Did (0,5) and (5,0) satisfy both equations when you substituted ? If so then you are correct.
*June 5, 2016*

**Math-SineLaw**

You are right, you have to use the sine law Since you know 2 angles, we can find the angle at F to be 51.2° So AF/sin87.3 = 34.32/sin51.2 AF = 34.32sin87.3/sin51.2 calculator time ..... AF = 43.988... repeat similar steps to find BF
*June 5, 2016*

**Math**

LS = 1 + (e^(2x) - 2e^0 + e^(-2x) )/4 = (4 + e^(2x) - 2 + e^(-2x) )/4 = ( e^(2x) + 2e^0 + e^(-2x) )/4 = ( (e^x + e^-x)/2 )^2 = RS
*June 5, 2016*

**Math**

What elements do you see in U which are NOT in T ?
*June 5, 2016*

**math**

1 litre = 10^3 cm^3 or 1000 cm^3 10 litres = 10,000 cm^3 I will assume your tank is 80 cm by 60 cm by 50 cm, and not 0.6 and 0.5 cm like you typed volume = 80(60)(50) cm^3 = 240000 cm^3 time for the given rate = 240000/10000 seconds = 24 seconds
*June 5, 2016*

**Math w/reply**

Thanks Bob for clearing that up. I was curious and checked some of my bottles of Tylenol etc, none of them up here in Canada have units such as grains, it is all in mg.
*June 5, 2016*

**maths**

"unit digit is 4" ----> X4 "tens digit is multiple of 3" ---> 34, 64, 94 "sum of digits is odd" ---> 34 or 94
*June 5, 2016*