X, Y are two points in a river. Points P and Q divide the straight line XY into three equal parts. The river flows along XY and the time taken by a boat to row from X to Q and from Y to Q are in the ratio 4 : 5. The ratio of the speed of the boat downstream to that of the river current is equal to:

Question

Question

This question was previously asked in

SSC CGL 2020 Tier-I Official Paper 1 (Held On : 13 Aug 2021 Shift 1)

Answer 1

F1 Ashish Madhu 19.10.21 D4

Given:

XP = PQ = QY

Ratio of time taken by boat to go from X to Q and Y to Q = 4 : 5

Formulas used:

Speed of the boat going downstream = (Speed of the boat + Speed of the current)

Speed of the boat going upstream = (Speed of the boat - Speed of the current)

Time = Distance/Speed

Calculation:

Let XP = PQ = QY = d

Let the speed of the boat = a km/h

Let the speed of the current = b km/h

As per the question:

2d/(a + b) ÷ d/(a - b) = 4/5

⇒ 2(a - b)/(a + b) = 4/5

⇒ 14b = 6a

⇒ a/b = 7/3

Speed of the boat downstream = (7 + 3) = 10

Speed of the current = 3

∴ The required ratio = 10 : 3

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