Multiple choice

A boat moves downstream at the rate of 1 km. in 7.5 minutes and upstream at the rate of 5 km. an hour. The speed of boat (in km./hr.) in still water is -

  1. 6.5

  2. 8.5

  3. 7.5

  4. 5.5

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Downstream speed = 1 km/7.5 min = 8 km/hr. Upstream speed = 5 km/hr. Let b = boat speed, c = current speed. b+c=8, b-c=5. Adding: 2b=13, so b=6.5 km/hr.