25.A boat, when sailing up the stream, takes 25minutes to cover a dist

1.	25.A boat, when sailing up the stream, takes 25minutes to cover a distance of 2 km and takes 20minutes to return. The speed of the stream is(A) 1.2 km/h(B) 1.1 km/h(C) 0.8 km/h(D) 0.8 km/h
Answer» Let the speed of stream be uLet speed of boat in still water be v Time taken to cover 2 km distance upstream =2/v - u = 25/60 = 5/125v - 5u = 24........ (1) Time take to cover 2 km distance downstream =2/v + u = 20/60 = 1/3v + u = 6............. (2) Multiply eq(2) by 55v + 5u = 30....... (3) Add eq(1) and eq(3)10v = 54v = 5.4 km/hr Put value of v in eq(2)v + u = 6u = 6 - 5.4u = .6 km/hr Therefore, speed of stream = .6 km/hr

25.A boat, when sailing up the stream, takes 25minutes to cover a distance of 2 km and takes 20minutes to return. The speed of the stream is(A) 1.2 km/h(B) 1.1 km/h(C) 0.8 km/h(D) 0.8 km/h

Answer»

Let the speed of stream be uLet speed of boat in still water be v

Time taken to cover 2 km distance upstream =2/v - u = 25/60 = 5/125v - 5u = 24........ (1)

Time take to cover 2 km distance downstream =2/v + u = 20/60 = 1/3v + u = 6............. (2)

Multiply eq(2) by 55v + 5u = 30....... (3)

Add eq(1) and eq(3)10v = 54v = 5.4 km/hr

Put value of v in eq(2)v + u = 6u = 6 - 5.4u = .6 km/hr

Therefore, speed of stream = .6 km/hr