Question

Amar went to Rishikesh for rafting. He faced an accident and his boat got punctured, so he called for help. Hearing this, a lifesaver who can row 24 km/h in still water left the tent to rescue Amar and it took him 1 hour to row to the accident site and come back. If the river is running at 3.6 km/h, how far is the accident site from the tent.

1. 12.45 km
2. 10.75 km
3. 5.76 km
4. 11.73 km

Answer 1

Correct Answer - Option 4 : 11.73 km

Given:

Speed of lifesaver in still water = 24 km/h

Time taken to travel downstream and upstream = 1 hour

Speed of river = 3.6 km/h

Formula used:

If the speed of boat in still water is x km/h and speed of the stream is y km/h, then

Speed of downstream = (x + y) km/h

Speed of upstream = (x – y) km/h

Calculation:

Let the distance between the tent and accident site be ‘D’

Lifesaver’s downstream rate = (24 + 3.6) = 27.6 km/h

Lifesaver’s upstream rate = (24 – 3.6) = 20.4 km/h

According to the question,

⇒ D/27.6 + D/20.4 = 1

⇒ 20.4D + 27.6D = 1 × 20.4 × 27.6

⇒ 48D = 563.04

⇒ D = 563.04/48 = 11.73 km

∴ The distance between the tent and the accident site is 11.73 km