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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