QA – Placement Quizzes | Progressions | Question 11

If the average of the given 7 consecutive numbers is x. Now, the next three numbers are also added, what effect will it have on the calculated average?

(A)

Remain unchanged

(B)

Increase by 1

(C)

Increase by 1.5

(D)

Increase by 2

Answer: (C)

Explanation:

We are given x = [(a-3)+(a-2)+(a-1)+a+(a+1)+(a+2)+(a+3)]/7 assuming that the middle number is a. Then, x = 7a/7 = a. If we add, the next three integers then the average becomes y = {[(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 y-x = 1.5

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