Question

Speed of a boat in still water is 15 km/h. It goes 30 km upstream and
returns back at the same point in 4 hours 30 minutes. Find the speed of the
stream.

Answer 1

Answer:

let x=speed of stream

(15+x)=speed of boat downstream

(15-x)=speed of boat upstream

travel time=distance/speed

30/(15+x)+30/(15-x)=9/2

60/(15+x)+60/(15-x)=9

LCD: (15+x)(15-x)

60(15-x)+60(15+x)=9(15+x)(15-x)

60(15-x+15+x)=9(225-x^2)

60(30)=2025-9x2

9x^2=2025-1800

9x2=225

take sqrt of both sides

3x=15

x=5

speed of stream=5 km/hr

Answer 2

Answer:

The correct answer is 5.

Hope this will help you.