2006 AMC 8 Problem 21

Attempt Problem 21 of the 2006 AMC 8 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2006 AMC 8 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

21.

An aquarium has a rectangular base that measures 100100 cm by 4040 cm and has a height of 5050 cm. The aquarium is filled with water to a depth of 3737 cm. A rock with volume 1000 cm31000\text{ cm}^3 is then placed in the aquarium and completely submerged. By how many centimeters does the water level rise?
0.250.25
0.50.5
11
1.251.25
2.52.5
Answer: A
Concepts:volumerectangular prism
Small hint:
A submerged object raises the water by its own volume.
Big hint:
Divide the rock’s volume by the base area of the aquarium.
Solution:
The base area of the aquarium is 100⋅40=4000 cm2100\cdot 40=4000\text{ cm}^2.
The submerged rock displaces 1000 cm31000\text{ cm}^3 of water, so the water level rises by 1000÷4000=0.251000\div 4000=0.25 cm.
Thus, A is the correct answer.
LIVE by Po-Shen Loh
Programs

LIVE Classes

Self-Paced Classes

Stars

Scholarship

About Us

Who Is Po-Shen Loh?

Email Contact

Newsletter

Jobs

Become a Star

For a more Thought Full world.

© 2026 Expii, Inc.