# Math Help - Scale Factor

1. ## Scale Factor

I'm having trouble with scale factor, particularly these two problems.

The areas of the bases of two similar square pyramids have the ratio 25:9. What is the ratio of their volumes?

The volumes of two similar rectangular prisms are in a ratio of 81:3000. Find the surface area of the larger solid if the smaller is 126m^2.

2. ## Re: Scale Factor

Originally Posted by Destroyer0203
I'm having trouble with scale factor, particularly these two problems.

The areas of the bases of two similar square pyramids have the ratio 25:9. What is the ratio of their volumes?

The volumes of two similar rectangular prisms are in a ratio of 81:3000. Find the surface area of the larger solid if the smaller is 126m^2.

If you scale a shape's side length by some factor (k), then its area is scaled by the square of that scale factor (k^2) and its volume is scaled by the cube of the scale factor (k^3). In the first, you know something about how the areas are scaled. Can you work out how the side lengths are scaled? From there can you work out how the volumes are scaled?

3. ## Re: Scale Factor

so if you have the area you could do the square root so you get 5:3 then since its volume you cube it and get 125:27?

Yes

5. ## Re: Scale Factor

ok, so i get the first one, how would you approach the 2nd one?

6. ## Re: Scale Factor

Originally Posted by Destroyer0203
ok, so i get the first one, how would you approach the 2nd one?
All the information you need is in my previous post.