Question

20. A boat travels 12 km upstream in 3 hours and
travels 25 km downstream in 2-hours. Find
2
the speed of the boat in still water and the speed
of the stream.​

Answer 1

Answer:

Let's Boat's Speed be x and Stream's Speed be y

⇒ Distance = Upstream × Time

⇒ 12 km = (x - y) × 3 hr

⇒ 12 km / 3 hr = (x - y)

⇒ (x - y) = 4 km/hr — ( I )

⇒ Distance = Downstream × Time

⇒ 25 km = (x + y) × 2 hr

⇒ 25 km / 2 hr = (x + y)

⇒ (x + y) = 12.5 km/hr ⠀— ( II )

• Solving equation I & II :

⇢ x + y = 12.5

⇢ x - y = 4

_____________

⇢ 2x = 16.5

⇢ x = 16.5 / 2

⇢ x = 8.25 km/hr [ Boat's Speed ]

⇢ x + y = 12.5

⇢ y = 12.5 - 8.25

⇢ y = 4.25 km/hr ⠀[ Stream's Speed ]