[Question]: John carves a giant marble rectangular prism 8 meters tall with a 2-meter square base. It has a density of 2700 kg per cubic meter. How much does it weigh?
[Answer]: The marble statue has a volume of 2 * 2 * 8 = 32 cubic meters. So that means it has a weight of 2700 * 32 = 86,400 kg.
So the answer is 86400.

[Question]: Grace can read a 200-page book in 20 hours. How long would it take her to finish reading a 250-page book at this constant rate?
[Answer]: Grace can read 200 / 20 = 10 pages in 1 hour. So she can finish a 250 - page book in 250 / 10 = 25 hours.
So the answer is 25.

[Question]: Mandy started reading books with only 8 pages when she was 6 years old. By the time she was twice that age, she was reading books 5 times longer, and 8 years later, she was reading books 3 times longer than that. Presently, she reads books that are 4 times the previous length. How many pages do the books she reads now have?
[Answer]:
Twice the age of 6 is 6 x 2 = 12 years old. At 12 years old, Mandy was reading books 5 x 8 = 40 pages long. 8 years later, Mandy was 12 + 8 = 20 years old. At 20 years old, Mandy was reading books 3 x 40 = 120 pages long. Presently, she reads books that are 120 x 4 = 480 pages long.
So the answer is 480.