The average age of 18 persons in a office is 15 years. Out of these, the average age of 5 of them is 14 years and that of the other 9 persons is 16 years. The age of the 15th person is? Select the correct option
A) 9	B) 31	C) 56	D) 72	E) 90

Rationale: age of the 15 th student = 18 * 15 - ( 14 * 5 + 16 * 9 ) = 270 - 214 = 56 years answer is c
Answer: C