Correct Answer - Option 2 : 14 hours

**Given:**

Distance covered upstream = 24 km

Distance covered downstream = 20 km

Speed of boat in still water = 6 km/hr

Speed of stream = 4 km/hr

**Concept used:**

Upstream speed = Speed of boat in still water – Speed of stream

Downstream speed = Speed of boat in still water + Speed of stream

**Calculation:**

Upstream speed = (6 – 4) km/hr

⇒ 2 km/hr

Downstream speed = (6 + 4) km/hr

⇒ 10 km/hr

Time taken to cover 24 km upstream = 24/2 hours

⇒ 12 hours

Time taken to cover 20 km downstream = 20/10 hours

⇒ 2 hours

Total time taken to cover the whole journey = (12 + 2) hours

⇒ 14 hours

**∴ The total time taken to cover whole journey is 14 hours**