Solution: the average monthly growth rate of turnover from March to May is X.

400×﹙ 1+ 10﹚×﹙ 1+x﹚？ =633 6

x= 1.2- 1

X = 0.2 = 20% or x =-2.2 (give up)

A: The average monthly growth rate of turnover from March to May is 20%.