A boy's speed with the current is 15 km/h and the speed of the current is 2.5 km/h. The boy's speed against the current is :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 10 km/h
Boys speed in water, b
Speed of the current, $c=2.5km/h$
Boys speed with current, $b+c=15km/h$
$⇒b+c=15$
$b=15-2.5=12.5km/h$
∴ Boys speed against current = $b-c$
$=10km/hr$