Anaira Mitch wrote:What is the minimum percentage increase in the mean of set X {-4, -1, 0, 6, 9} if its two smallest elements are replaced with two different primes?
(A) 25% (B) 50% (C) 75% (D) 100% (E) 200%
Current mean = sum/number = [-4 + (-1) + 0 + 6 + 9]/5 = 10/5 = 2.
The smallest elements in the set are -4 and -1.
To minimize the increase in the mean, the prime numbers chosen to replace -4 and -1 must be as small as possible.
Smallest distinct primes that could replace -4 and -1 are 2 and 3.
New mean = (new sum)/number = (2 + 3 + 0 + 6 + 9)/5 = 20/5 = 4.
From 2 to 4 is an increase of 100%.
The correct answer is
D.
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