A boy walks from his house at 4 km per hr. and reaches his school 9 minutes late. If his speed had been 5 km per hr. he would have reached his school 6 minutes earlier. How far his school from house?

(1) 6.5 km. (2) 5.5 km. (3) 6 km. (4)5 km.

Solution:

Let time taken to reach school at 4 kmph be x hrs.
Then time taken to reach school

at 5 kmph = (x+15/60)hrs

Since, distance is equal.

,’. 4x=5(x+15/60)

x= 5/4 hrs.

Hence, distance between school & house = 4*5/4km= 5km

Then the answer is 5km.