11. Three different positive integers have a mean of 7. What is the largest positive integer that could be one of them?
A 15
B 16
C 17
D 18
E 19
11. D As the 3 numbers have mean 7 , their sum equals $3 \times 7=21$. For one of the numbers to be as large as possible the other two numbers must be as small as possible. They must also be different and so must be 1 and 2 . Hence the largest possible of the three numbers equals $21-(1+2)=18$.