Question

If the upstream speed of boat and speed of stream is in the ratio of 5 : 1 and the time taken to cover the distance of 140 kms in upstream is 2 hours more than downstream then find the speed of boat in still water ?
1. 28 kmph
2. 20 kmph
3. 12 kmph
4. 24 kmph
5. 22 kmph

Answer 1

Correct Answer - Option 4 : 24 kmph

GIVEN:

⇒ Total distance = 140 kms

ASSUMPTION:

Let the upstream speed of Boat and speed of the stream be 5x and 1x.

⇒ Speed of boat in still water = 5x + 1x = 6x

⇒ Downstream speed = 6x + 1x = 7x

CALCULATION:

According to the question.

When travelling downstream.

⇒ Let the time taken = T hours

⇒ 7x = 140/T      ----(1)

When travelling upstream.

Let the time taken = (T + 2) hours

⇒ 5x = 140/ (T + 2)      ----(2)

From eq(1) and eq(2)

⇒ T = 5 hours

⇒ x = 4

⇒ Speed of Boat in still water = 6x = 6 x 4 = 24 kmph