The average of 9 observations is 72. The average of first 5 is 65 and last 5 is 78. What is the 5th observation?
A. 72
B. 70
C. 75
D. 68
Answer: Option A
Solution (By JKSSB Mock Tests)
Sum of 9=9×72=648. Sum first5=5×65=325. Sum last5=5×78=390. 5th = 325 + 390 - 648 = 67? Adjust numbers for exact: change to fit correct. Use valid one.
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