Statement: 9 periods in a school.

Total no. of periods = 9

Statement: Each period takes 40 mins.

Duration of each period = 40 mins

Total school hours = 360 mins or 6 hrs

Problem: how long would each period be if the school has 8 periods a day assuming the number of school hours to be the same?

Suppose that we do not know each period's duration. We only know the total school hour, then what would we do to find the answer. ---

360/9 = 40

The thing is to divide the total duration by the no. of periods to find individual period duration.

Similarly, to find the individual period duration of 8 periods, we will do -

360/8 =   45


So, 45 mins is the answer.