Question

A swimmer covers a distance 20 km against the current and 30 km in the direction of current. If in each case he takes 5 hours, then the speed of the current is
1. 1 km/hr
2. 2 km/hr
3. 3 km/hr
4. None of the above

Answer 1

Correct Answer - Option 1 : 1 km/hr

Given:

Swimmer speed along the current = 30 km

Swimmer speed against the current = 20 km

Time is taken = 5h in each case 

Formula used:

Speed of current = (downstream speed - upstream speed)/2

Downstream speed = distance travelled along the current/time taken

Upstream speed = distance travelled against the current/time taken

Calculations:

Downstream = 30/5

⇒ 6km/hr

Upstream speed = 20/5

⇒ 4 km/hr

Speed of current = (6 - 4)/2

⇒ 2/2 = 1 km/hr

∴ The speed of current is 1 km/hr