LIC AAO Model Paper 6

Question : 38 of 160

Marks: +1, -0

A boat takes 3 hours less time in rowing from point X to point Y in downstream than that in rowing from point Y to point Z in upstream. The distance between X and Y is 20 km which is half of the distance between Y and Z. Speed of boat B in still water is 10 kmph. The speed of boat A in still water is equal to the rate upstream of boat B. What is the speed of boat A in still water? (in kmph).

Validate

Solution:

Speed of current = xkmph (let)
Rate Upstream of boat B = (10 -x) kmph
Rate downstream of boat A = 10-x+x = 10 kmph
∴

{40}/{10-x}

{20}/{10}

= 3
⇒

{40}/{10-x}

= 5
⇒ 50 - 5x = 40
⇒ 5x = 50 - 40 = 10
⇒ x =

{10}/5

= 2 kmph
∴ Speed of boat A in still water
= 10 - 2 = 8 kpmh

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