CEMC Fermat, 2003

Geometry Difficulty 1.0 Junior Find the answer Canada

A fish tank, in the shape of a rectangular prism, has a base measuring 20 cm by 40 cm with a height of 30 cm. The tank sits on a horizontal table and is half full of water. If 4000 cm $^3$ of water is added, what is the new depth of the water?

(A) $5$ cm (B) $15$ cm (C) $20$ cm (D) $25$ cm (E) $10$ cm

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