Wednesday
June 29, 2016

Posts by Reiny

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

Pre-Algebra
yes
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

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