Question

A marble paperweight shaped similar to a prism weighs 0.3 lb. How much does a similarly shaped marble paperweight weigh if its length, width, and height are doubled?

Answer 1

Maybe it's 2.4 lb. just a guess.

Answer 2

Short Answer
8 times as much <<<<< answer

Don't get caught by saying the new weight will be double the old one.
It isn't so.

Argument
Let the first paper weight have a volume calculated from
V = L * W * H
W = weight = 3 pounds.
density = W / V

The density is the same in both cases. It is made of marble.

New Volume
V1 = 2L * 2W * 2 H
V1 = 8 * L * W * H

W/V = W1 / V1
0. 3 / ( L * W * H) = x / (8 *L * W * H) Cross Multiply
0.3 * 8 * L * W * H = x * L * W * V
2. 4 * L * W * H = x * L * W * V Divide both sides by L * W * H
2.4 = W1

The new paper weight will be 2.4 pounds.
2.4 pounds <<<< answer.