Question

boat goes 75 km downstream and 60 km upstream in 6 hours, while it can go 100 km

downstream and 40 km upstream at the same time, find the speed of the stream and speed

of the boat in still water.​

Answer 1

Step-by-step explanation:

boat velocity in downstream = distance/ time taken = 75/6 km/ hr = 25/2km/hr

and upstream = 60/6= 10km/hr

let boat velocity in still water = x km/hr

and stream velocity = y km / hr

so boat velocity of downstream = x+y

or 25/3= x+y,,,,,,,1

and boat velocity of downstream = x-y

or 10= x-y ,,,,,,,,,2

eqn 1 + 2

x+y+x-y = 25/2+10

or 2x = (25+20)/2

or x = 45/(2×2) =45/4km/hr

and y = x-10( from 2eqn)

or y = 45/4 -10 = 5/10 = 1/2 km/hr

boat velocity in still water = 45/4 km/hr and still water = 1/2 km/hr