A certain list consists of 21 different numbers. If n is in the list and n is 2 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?  Choose the correct choice from the following answers:  A) 1/20  B) 1/6  C) 1/11  D) 4/21  E) 5/21
series : a1, a2....a20,n   sum of a1+a2+...+a20 = 20*x (x = average)   so, n = 2*x   Hence, a1+a2+..+a20+n = 22x   So, the fraction asked = 2x/22x = 1/11   Answer 1/11
<result>C</result>
A certain list consists of 21 different numbers. If n is in the list and n is 2 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?