100 m/min - 60 m/min = 40 m/min

When running, he can travel 40 m more every minute compared to walking.

2 minutes early vs 6 minutes late :

Time difference = 6 min + 2 min = 8 min

So if he runs to school, he will reach 8 min faster than if he walks the same distance.


8 min × 60 m/min = 480 m

So if he had walked instead of running, he would still have another 480m to walk after the same amount of time (as compared to running, where he would have already reached school)

This means that for the same amount of time, distance travelled by running was 480m more than walking.

480m ÷ 40 m/min = 12 min

This tells us that in 12 minutes, distance travelled by running was 480m more than walking.

Which implies that he would use 12 min to run to school.

Since running makes him 2 min early, time he would take to reach on time
= 12 min + 2 min
= 14 min

Distance from home to school
= 12 min × 100 m/min
= 1200 m

Speed he needs to travel to be on time
= 1200 m ÷ 14 min
= 85 5/7 m/min
= 86 m/min (nearest m)

Check :

Time taken to walk to school
= 1200 m ÷ 60 m/min
= 20 min

Difference between time taken to walk compared to running
= 20 min - 12 min
= 8 min ✔

Alternatively, imagine this scenario :

If he had continued to run for that 8 min instead of just stopping at school,

Distance travelled
= 8 min × 100 m/min
= 800 m

So, in the same amount of time he walked to school, he would have travelled 800m more by running.

800 m ÷ 40 m/min = 20 min

This means that in 20 min, distance travelled by running was 800 m more than walking.

Which implies that he used 20 min to walk to school.

Distance from home to school
= 60 m/min × 20 min
= 1200 m

The rest is the same working.

Thank u J .