Question

A boy leaves his house at 9.30 am for his school.the school is 2km away and classes start at 10.00am.if he walks at a speed of 3km/h for the first kilometre at what speed should he walkthe second kilometre to reach just in time

Answer 1

if he walks by 3km/h for first km he will reach 1km in 20min.
now time left is 40min and he has to cover 1km distance.
he should walk by 1km/40min

Answer 2

He should reach the school in half an hour (= 30 minutes).

Time taken by him to travel 1st kilometer is
T = Distance / Speed
= 1 km / 3km/h
= 1/3 hours

Time left for him to travel next kilometer = 1/2 - 1/3 = 1/6 hours
Speed = Distance / Time
= 1 km / (1/6 h)
= 6 km/h

He should travel with speed of 6 km/h to just reach the school on time.