Answer:
40 min per period
Step-by-step explanation:
When it has 8 periods :
Total time = 45 min per period for 8 period
Total time = 45 × 8 min
When it has 9 periods : let each period be of x min
Total time = x min per period for 9 period
Total time = x × 9 min
As total time remains same,
45 × 8 = x × 9
5 x 8 = x
40 = x
