The average of 6 observations is 11. A new observation is included and the new average is decreased by 1. The seventh observation is?  Select the correct option:
A) 4
B) 3
C) 5
D) 6
E) 7

Rationale: "let seventh observation = x . then , according to the question we have = > ( 66 + x ) / 7 = 10 = > x = 4 . hence , the seventh observation is 4 . answer : a"
Answer: A