**Question:**

*Tick (✓) the correct answer:*

Two pipes can fill a tank in 20 minutes and 30 minutes respectively. If both the pipes are opened simultaneously, then hte tank will be filled in

(a) 10 minutes

(b) 12 minutes

(c) 15 minutes

(d) 25 minutes

**Solution:**

(b) 12 minutes

First pipe can fill a tank in 20 minutes.

Second pipe can fill the tank in 30 minutes.

Part of tank filled by the first pipe in one minute $=\frac{1}{20}$

Part of tank filled by the second pipe in one minute $\frac{1}{30}$ Part of tank filled by both pipes in one minute $=\frac{1}{20}+\frac{1}{30}=\frac{5}{60}=\frac{1}{12}$

Thus, it takes 12 minutes to fill the tank using both the pipes.

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