Question

Speed of a boat is 25 km per hour in still water and the speed of the stream is 5 km per hour. If the boat takes 15 hrs to go to a place and come back, the distance of the place is (SBI Clerk 2019)

Answer 1

Answer:

180 km

Step-by-step explanation:

Speed of boat is 25 km /h

Speed of stream is 5 km/h

Let the distance between the two places be d

When boat is moving upstream

the speed is

(25-5)km/h

20 km/h

Hence time taken to cover the distance d = d/20

When boat us moving downstream

the speed is

(25+5) km/h

30 km/h

Hence time taken to cover distance d again = d/30

Total time to go downstream and upstream once is

15 hours

This implies that

d/20 + d/30 = d (1/20 + 1/30) = 15

d(30 + 20/30 × 20) = 15

d(50/600) = 15

d(1/12) = 15

d = 15 × 12

d = 180 km