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XAT 2021 — QA & DI Question 9

Boats and StreamsEasy

Swati can row a boat on still water at a speed of 5 km/hr. However, on a given river, it takes her 1 hour more to row the boat 12 km upstream than downstream. One day, Swati rows the boat on this river from X to Y, which is N km upstream from X. Then she rows back to X immediately. If she takes at least 2 hours to complete this round trip, what is the minimum possible value of N?

Answer & solution

  • A

    3

  • 4.8

  • C

    2

  • D

    3.6

  • E

    2.1

Solution

Let the speed of the stream be x

Let the speed of the stream be 

125-X = 125+X + 1

The value of x satisfying the above equation is 1
Now,

N5+1 + N5-1 ≥ 2

2N+3N12 ≥ 2

⇒ N ≥ 4.8

XAT 2021 QA & DI Q9: Swati can row a boat on still water at a speed of 5 km/hr. However, on a given river, it takes her 1 hour more — Solution | TheCATExam