QA – Placement Quizzes | Progressions | Question 11

The average of 7 consecutive number is P. If the next three numbers are also added, the average shall:
(A) Remain unchanged
(B) Increase by 1
(C) Increase by 1.5
(D) Increase by 2


Answer: (C)

Explanation: We are given P = [(a-3)+(a-2)+(a-1)+a+(a+1)+(a+2)+(a+3)]/7 assuming that the middle number is a. Then,
P = 7a/7 = a.
If we add, the next three integers then the average becomes
Q = {[(a-3)+(a-2)+(a-1)+a+(a+1)+(a+2)+(a+3)] + [(a+4)+(a+5)+(a+6)]}/10 = {7a + 3a + 15}/10 = {10a + 15}/10 = a + 1.5.
So, the average is increased by Q-P = 1.5

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