A certain list consists of 21 different numbers. If n is in the list and n is 8 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?
Pick
A) 1/20	B) 1/6	C) 2/7	D) 4/21	E) 5/21
series : a1, a2....a20,n   sum of a1+a2+...+a20 = 20*x (x = average)   so, n = 8*x   Hence, a1+a2+..+a20+n = 28x   So, the fraction asked = 8x/28x = 2/7   2/7
<result>C</result>
A certain list consists of 21 different numbers. If n is in the list and n is 8 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?