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? Select
A) 1/20  B) 1/12  C) 1/5  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 = 1/12   1/12
<result>B</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?