Correct Answer - Option 2 : 16 minutes

**Given:**

A tap fills a cistern in 8 minutes and another tap empties it in 16 minutes

**Calculation**

Time taken to fill the cistern = 8 min

Part of cistern filled in 1 min = 1/8

Time taken to empty the cistern = 16 min

Part of cistern emptied in 1 min = 1/16

When both taps are opened simultaneously,

Part of cistern filled in 1 min = 1/8 - 1/16

⇒ 1/16

Time taken by both taps to fill the cistern = 16 minutes