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Mean - Question

by MI3 » Sun Jul 17, 2011 2:48 am
Q. If numbers N and K are added to set X {2, 8, 10, 12}, its mean will increase by 25%. What is the value of N^2 + 2NK + K^2 ?
(A) 28 (B) 32 (C) 64 (D) 784 (E) 3600

IMO D, am I correct?
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by MBA.Aspirant » Sun Jul 17, 2011 3:03 am
MI3 wrote:Q. If numbers N and K are added to set X {2, 8, 10, 12}, its mean will increase by 25%. What is the value of N^2 + 2NK + K^2 ?
(A) 28 (B) 32 (C) 64 (D) 784 (E) 3600

IMO D, am I correct?

mean = 32/4 = 8

mean ^ 25% = 10

sum = 10*6 = 60

n+k = 60 -32 = 28

n^2 +2nk +k^2 = (n+k) (n+k) = 28 * 28 = 784
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by amit2k9 » Mon Jul 18, 2011 10:38 pm
(N+K + 32)/6 = 8*1.25 = 10

thus N+K = 60-32 = 28

hence (N+K)^2 = 784
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