The average of 13 numbers is 14.8. If the average of the first seven numbers is 14.6 and that of the last seven numbers is 14.4,then the middle number is?
Choices.
A) 11.6 B) 12.6 C) 10.6 D) 9.6 E) 8.6
Middle number = 14.6*7 + 14.4*7- 14.8*13 = 102.2+100.8-192.4= 
<gadget id="calculator">102.2+100.8-192.4</gadget>
<output>10.6</output>
10.6   Answer is 10.6
<result>C</result>
The average of 13 numbers is 14.8. If the average of the first seven numbers is 14.6 and that of the last seven numbers is 14.4,then the middle number is?