A boat racer can row 21\(\frac{3}{2}\) km/h in still water. If the speed of river is 12.5 km/hr, it takes him 40 minutes to row to a place and back, how far off is the place (consider up to two decimals)?

Question

Question

This question was previously asked in

SSC CGL 2022 Tier-I Official Paper (Held On : 06 Dec 2022 Shift 1)

Answer 1

Given:

A boat racer can row 21\(\frac{3}{2}\) km/h in still water.

The speed of the river is 12.5 km/hr, it takes him 40 minutes to row to a place and back.

Calculations:

Let the distance be x, then,

Upstream speed

⇒ 21\(\frac{3}{2}\) km/h - 12.5 km/h

⇒ 22.5 - 12.5

⇒ 10 km/h

Downstream speed

= 22.5 km/h + 12.5 km/h

= 35 km/h

According to the question,

x/10 + x/35 = 40/60

⇒x(1/10 + 1/35) = 2/3

⇒x(45/350) = 2/3

⇒x = 2 × 70 / 3 × 9

⇒x = 5\(\frac{5}{27}\) km

Hence , The Required value is 5\(\frac{5}{27}\) km.