The average of 6 observations is 13. A new observation is included and the new average is decreased by 1. The seventh observation is?  Select the correct option:  A) 1  B) 3  C) 5  D) 6  E) 7
Let seventh observation = X.   Then, according to the question we have   =&gt; (78 + X) / 7 = 12   =&gt; X = 6.   Hence, the seventh observation is 6.   ANSWER:6
<result>D</result>
The average of 6 observations is 13. A new observation is included and the new average is decreased by 1. The seventh observation is?