# Interesting Geometry Probem

posted by
**Elizabeth**
.

I am bulding a sculpture out of rock and need help figuring out how much rock to buy... Here are the figures...

1 ton of 1.5" rock covers 107 sq. ft.

My sculpture will be comprised of 24 layers of rock 2" thick. Each layer will be aproximatly 3ft. by 3ft. How many tons of rock do I need?

How does one figure this answer? Thank you.

It doesn't really sound like you are making a sculpture. I don't know of any sculptures that are made with "layers of rock." It's okay to say you want help with a geometry problem that has been assigned. If my knowledge of sculptures is lacking, you have my apologies.

Since the 2" thick rock has 24 layers, you are looking for a depth of 48". 48" divided by 1.5" = 32 layers of 1.5" stone that are needed.

Since each layer is 9 square feet, multiply the layers by 32. Then divide that by 107 to get the number of tons that will be needed.

I hope this helps. Thanks for asking.

Another way to do this is density.

The density of rock is 1ton/volume where volume is 107*(1.5/12) ft^3.

This density will not vary in the second problem. Calculate out the density.

amount of rock = density*24*(2/12)*3*3