Question

A boat moves down the stream at the rate of 1 km in 6 minutes and up the stream at the rate of 1 km in 10 minutes. The speed of the current is
1. 2 km/hr
2. 3.5 km/hr
3. 3 km/hr
4. 2.5 km/hr

Answer 1

Correct Answer - Option 1 : 2 km/hr

Let speed the boat and current be x km/hr and y km/hr.

Downstream speed = (x + y) km/hr

Upstream speed = (x – y) km/hr

For down the stream,

6 min → 1 km

60 min or 1 hr → 10 km

For up the stream,

10 min → 1 km

60 min or 1 hr = 6 km

According to the question,

(x + y) = 10     ...1)

(x – y) = 6     ...2)

From equation (1) and equation (2),

y = 2 km/hr

So, speed of the current = 2 km/hr