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CEMC Gauss (Grade 7), 2011

Algebra Difficulty 2.0 Junior Find the answer Canada

A pool has a volume of $4000$ L. Sheila starts filling the empty pool with water at a rate of $20$ L/min. The pool springs a leak after $20$ minutes and water leaks out at $2$ L/min. Beginning from the time when Sheila starts filling the empty pool, how long does it take until the pool is completely full?

(A) $3$ hours (B) $3$ hours $40$ minutes (C) $4$ hours (D) $4$ hours $20$ minutes (E) $3$ hours $20$ minutes

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