The mode is the number that appears most in a set of numbers.
Put the set in numerical order, from least to greatest.
5, 8, 10, 10, 10, 11, 12, 12, 14, 17, 17,18, 19, 20, 20, 21
5 - |
8 - |
10 - |||
11 - |
12 - ||
14 - |
17 - ||
18 - |
19 - |
20 - ||
21 - |
There are three 10s, whereas there's only two or less sets of all the other numbers.
Answer:
The mode of the data set is 10.