1.

The average of thirteen numbers is 80. The average of the first five numbers is 74.5 and that of the next five numbers is 82.5. The 11th numbers is 6 more than the 12th number and the 12th number is 6 less than the 13th number. What is the average of the 11th and the 13th numbers?

A. 87
B. 87.5
C. 86
D. 86.5
Answer» B. 87.5


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