Solution 7: If the average annual growth rate of rice yield per hectare is X, the average rice yield per hectare in 2002 is 7200( 1+x) kg, and in 2003 it is 7200 (1+x) = 7200 (65438). 0? 5 kg; According to the meaning of the question, the equation can be listed as follows:

7200( 1+x)？ 0? 5=8450

( 1+x)？ 0? 5=8450/7200

( 1+x)？ 0? 5= 169/ 144

1+x = √( 169/ 144)

1+x= 13/ 12

1+x= 13/ 12 or1+x =-13/12 (irrelevant and should be omitted).

x= 1/ 12

A: The average annual growth rate of rice yield per hectare is112.