# By what factor help?

1. Apr 10, 2017

1. The problem statement, all variables and given/known data

2. Relevant equations
Cake one...
Area of circle times height
Pipe one... Av = Av

3. The attempt at a solution
Hello, i would like some help in the right direction/
I had a go at these problems and got B) for the pipe one and C for the cake one.
However the correct answers for the pipe one is A) whereas the one for the cake is E.).

I dont understand what im doing wrong. If you try substituting values and work backwards the constants i get dont fit.
EG: for the pipe one i made r = 4...
pi * 4^2 * 0.5 = pi* x * 4^2 * 2
x = 0.25 so i got B, but the correct answer is A...

For the cake problem i made h=5 and diametre = 8cm (radius = 4)...
pi * 4^2 * 5 = 251 m-3
i then doubled volume, and worked backwards to find factor to increase radius and therefore diamtre by...

502 = pi * r^2 * 5
r = 5.6418
5.6418/4 = 1.44... so i got C, but correct answer is E

2. Apr 10, 2017

### mjc123

Pipe: if x is the scaling of the radius, you should have pi*x^2*4^2*2
Cake: it is a scale model, so all dimensions increase by the same factor: pi*x^2*4^2*x*5 = 502

3. Apr 10, 2017