Subject: mathqa
Question: a certain list consists of 21 different numbers . if n is in the list and n is 4 times the average ( arithmetic mean ) of the other 20 numbers in the list , then n is what fraction t of the sum of the 21 numbers in the list ?
Option: 
A: 1 / 5
B: 1 / 6
C: 5 / 21
D: 4 / 21
Answer: B