1.

A boat can row 3 times as fast in downstream than in upstream. In still water the boat covers a distance of 50 m in 5 seconds. Calculate the time the boat will take to cover a distance of 45 km downstream.1. 180 minutes2. 120 minutes3. 100 minutes4. 50 minutes5. 45 minutes

Answer» Correct Answer - Option 4 : 50 minutes

Given:

Speed downstream is 3 times speed upstream.

In still water boat goes 50 m in 5 seconds.

Concept:

Speed downstream is sum of the speed of boat in still water and speed of stream

Speed upstream is difference of the speed of boat in still water and speed of stream.

To convert hours to minutes we have to multiply by 60

Formula:

Speed = distance/time

Time = distance/speed

Speed in m/s × 18/5 = speed in km/h

Calculation:

Speed of boat in still water = 50/5 = 10 m/s

Let the speed of stream be x m/s

Speed during downstream = (10 + x) km/h

Speed during upstream = (10 – x) km/h

3 × (10 – x) = (10 + x)

⇒ (10 – 3x) = (10 + x)

⇒ 3x + x = 30 – 10

⇒ 4x = 20

⇒ x = 5

Speed downstream = 10 + 5 = 15 m/s

Speed downstream = 15 × (18/5) = 54 km/h

Time to cover 45 km = 45/54 = (5/6) hours

Time taken to cover 45 km = (5/6)× 60 = 50 mins

 Time to cover the distance downstream is 50 minutes



Discussion

No Comment Found

Related InterviewSolutions