## Zara 3 years ago Two mathematically similar frustums have heights of 20cm and 30cm. The surface area of the smaller frustum is 450cm^2. Calculate the surface area of the larger frustum.

1. Zara

I understand that you have to multiply the smaller frustum's height by 1.5 to get the larger frustum's height, so do you just have to multiply the smaller frustum's area by 1.5 as well?

2. asnaseer

If the two solids are /similar/ then their surface area will be in a ratio that is the square of the ratio of any of their linear dimensions (e.g. height ratios). Similarly, their volumes will be in a ratio that is the cube of their ratio of linear dimensions

3. Zara

So you would do 450*1.5^2?

4. asnaseer

yes, but be careful with what you are squaring, it should be:$450\times(1.5)^2$

5. Zara

Yup that's what I meant :) Gracias!

6. asnaseer

yw :)