The average of 6 observations is 16. A new observation is included and the new average is decreased by 1. The seventh observation is?
Pick
A) 1
B) 3
C) 9
D) 6
E) 7

Rationale: "let seventh observation = x . then , according to the question we have = > ( 96 + x ) / 7 = 15 = > x = 9 hence , the seventh observation is 9 . answer : c"
Answer: C