Question

Speed of boat in still water is 15kmperhr it goes 30km upstream returns back at same point in 4hr 30min . Find speed of stream

Answer 1

Answer: speed of stream=5 km/hr

Step-by-step explanation:

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