A man rows upstream 15 km and downstream 18 km, he takes 3 hours each time. The speed of the current is:

Question

Question

This question was previously asked in

SSC GD Constable (2022) Official Paper (Held On : 16 Jan 2023 Shift 1)

Answer 1

Given data:

Distance travelled upstream = 15 km

Distance travelled downstream = 18 km

Time taken to travel upstream = Time taken to travel downstream = 3 hours

Formula Used:

Speed of the current = (Downstream speed - Upstream speed) ÷ 2

Calculation:

Calculate the speeds of man (m) and current (c)

⇒ Upstream speed = distance ÷ time = 15 km ÷ 3 h = 5 km/h (m - c = 5 km/h)

⇒ Downstream speed = distance ÷ time = 18 km ÷ 3 h = 6 km/h (m + c = 6 km/h)

Solving these equations for c:

⇒ c = (m + c - m + c) ÷ 2 = (6 km/h - 5 km/h) ÷ 2 = \(\frac{1}{2}\) km/h

Therefore, the speed of the current is \(\frac{1}{2}\) km/h.

Alternate Method Let, the speed of the boat = x

Speed of Stream = y

⇒ x + y = 6 km\hr

⇒ x - y = 5 km/hr

⇒ x = 11/2 km/hr and y = 1/2 km/hr.

∴ The speed of Current is 1/2 km/hr.

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