the average of 6 observations is 15 . a new observation is included and the new average is decreased by 1 . the seventh observation is ?
"let seventh observation = x . then , according to the question we have = > ( 90 + x ) / 7 = 14 = > x = 8 hence , the seventh observation is 8 answer : b"
subtract(multiply(subtract(15, 1), add(6, 1)), multiply(15, 6))