The ratio of the arithmetic mean of two numbers to one of the numbers is 5:7. What is the ratio of the smaller number to the larger number? Choose the most appropriate option
A) 2 : 3
B) 2 : 5
C) 3 : 7
D) 4 : 9
E) 5 : 6

Rationale: "for two numbers , the arithmetic mean is the middle of the two numbers . the ratio of the mean to the larger number is 5 : 7 , thus the smaller number must have a ratio of 3 . the ratio of the smaller number to the larger number is 3 : 7 . the answer is c ."
Answer: C