Answer:
20,000 fans
Explanation:
Since the large crowd participated in the band concert.
Also, it is given that averaging 21,359 fans participate in the band concert.
So, the most likely value lies nearly 21,359
and the value that is most near to 21,359 is 20,000
Also, 20, 200 and 2000 are very small values compare to 21,359.
Thus, the value most likely to be correct is: 20,000 fans.