1.

Rahul can row 25 km upstream in 5 hour. If the speed of Rahul in still water is 6km/hr. Find the distance he can row downstream in 20 hour.1. 120 km2. 140 km3. 160 km4. 158 km

Answer» Correct Answer - Option 2 : 140 km

Given

Speed of Rahul in still water (u) = 6 km/hr

Rahul rows 25 km upstream in 5 hours

Formula used

The speed of a boat in still water is u km/hr

The speed of the stream is v km/hr,

Speed downstream = (u + v) km/hr.

Speed upstream = (u - v) km/hr.

Calculation

Speed of water (v) =  km/hr

⇒ Speed in still water (u) = 6 km/hr

⇒ Upstream speed = 25/5 km/hr

⇒ 5 km/hr

Speed of Stream = (6 – 5) km/hr

⇒ 1 km/hr

Downstream speed = (6 + 1) km/hr

⇒ 7 km/hr

Distance travelled in 20 hour downstream

⇒ 7 × 20 = 140 km

∴ The required distance covered is 140 km.



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