Answers

2014-08-18T21:15:55+05:30
The mode is defined as the number occurring most no. of times.
or the number with highest frequency 

11 occurs 3 times
21 occurs 4 times
31 occurs 1 time
51 occurs 2 times

As 21 is occurring most times, so mode is 21

Answer
21
0
2014-08-18T21:25:32+05:30
Mode is 21 as it has highest frequency of 4
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