Correct Answer - Option 4 : 22 hours

**Given:**

Speed of boat in still water = 16 km/hr

Speed of the stream = 6 km/hr

Distance covered in downstream = 220 km

**Formulas Used:**

Time = Distance/Speed

S_{(upstream)} = S_{(boat)} - S_{(stream)}

**Calculation:**

S_{(upstream)} = S_{(boat)} - S_{(stream)}

⇒ S_{(upstream)} = (16 - 6) km/hr

⇒ S_{(upstream)} = 10 km/hr

Time = Distance/Speed

⇒ T = 220/10 hr

⇒ T = 22 hr

**∴ T****he time taken by boat is 22 hours**