Using the cross method to solve the mixed growth rate problem can be divided into two main steps:

1. The overall growth rate is between two parts.

2. The overall growth rate is biased towards the growth rate of the part with larger base period value.

for example, in February 2116, the catering revenue was 335.2 billion yuan, up 1.6% year-on-year, of which the catering revenue of units above designated size was 94.6 billion yuan, up 6.7% year-on-year.

Question: In February, 2116, the catering income of units below the quota increased year-on-year:

A.7.3% B.11.3% C.12.2% D.14.5%

Analysis: From the meaning of the question, it can be seen that catering income = catering income of units above the quota+catering income of units below the quota, then the growth rate of catering income is determined by catering income of units above the quota. 11.6%, excluding options A and B; In February 2115, the catering income of the above-designated units was 94.6/(1+6.7%) billion yuan <; The catering income of units above designated size is 3352/(1+11.6%)-946/(1+6.7%) billion yuan, which can be (6.7%+x%)/2 <; 11.6%, x% <; 14.5%, choose option C.