Correct Answer - Option 2 : 10 kmph
Given:
Distance travelled downstream = 9 km
Time taken in travelling downstream = 45 minutes
Speed of current = 2 kmph
Formula used:
Downstream speed = Speed of boat in still water + Speed of current
Calculations:
Downstream speed = 9 km/45 minutes
⇒ 9/(3/4)
⇒ 12 kmph
Speed of boat in still water = Downstream speed – Speed of current
⇒ 12 – 2
⇒ 10 kmph
∴ The speed of boat in still water is 10 kmph