A man rows 15 km upstream in 5 hours and 25 km downstream in 5 hours each time, then the speed of the stream is Option 1: 2 km / hour Option 2: 5 km / hour Option 3: 3 km / hour Option 4: 1 km/ hour

Answer: 1 km/ hour. Solution: When a man rows upstream, he goes against the water flow. When rowing downstream, he goes with the water flow. Given: - Upstream: 15 km in 5 hours - Downstream: 25 km in 5 hours Upstream speed = 15/5 = 3 km/h Downstream speed = 25/5 = 5 km/h Let the man's rowing speed in still water be m and the stream's speed be s. When going upstream, the stream slows him down: m - s = 3 ... (1) When going downstream, the stream speeds him up: m + s = 5 ... (2) Subtracting equation (1) from equation (2): (m + s) - (m - s) = 5 - 3 m + s - m + s = 2 2s = 2 s = 1 km/h The speed of the stream is 1 km/h.

Arithmetic

Time, Speed & Distance

Medium

applied

A man rows 15 km upstream in 5 hours and 25 km downstream in 5 hours each time, then the speed of the stream is

2 km / hour

5 km / hour

3 km / hour

1 km/ hour

✅ Correct Option: 4

When a man rows upstream, he goes against the water flow. When rowing downstream, he goes with the water flow.

Given:

Upstream: 15 km in 5 hours
Downstream: 25 km in 5 hours

Upstream speed $= \dfrac{15}{5}$

$= 3$ km/h

Downstream speed $= \dfrac{25}{5}$

$= 5$ km/h

Let the man's rowing speed in still water be $m$ and the stream's speed be $s$ .

When going upstream, the stream slows him down:

$m - s = 3$ ... (1)

When going downstream, the stream speeds him up:

$m + s = 5$ ... (2)

Subtracting equation (1) from equation (2):

$(m + s) - (m - s) = 5 - 3$

$m + s - m + s = 2$

$2s = 2$

$s = 1$ km/h

The speed of the stream is $1$ km/h.

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Solution

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