Mode: the number that occurs the most in a set of data.
Although it's optional, I always like to order the numbers from least to greatest so it makes it easier to see what number repeats more than anything else.
Least to greatest - 40,41,42,43,44,45,46,47,48,49,49
The mode for this set of data is 49. The mode is 49 because 49 is the only number that occurs more than once. No other numbers in this set of data appear twice except 41.