A man reduces his speed from 20 kmph to 18 kmph. So, he takes 10 minutes more than the normal time. what is the distance traveled by him.

Explanation:-

Usual time = 9 * 10 = 90 min = ³/₂ h
Thus,
Distance traveled = Speed * time = 20 * (³/₂) = 30 km.

Alternatively,
As the speed decreases from 20 kmph to 18 kmph i.e. 10 % increment in usual time.
10 % = 10 min
100 % = 100 min.
Now,
Distance traveled by him,
= (¹⁰⁰/₆₀ h) *18
= 30 km.