The definition of mode - The most frequently appearing number in a data set.
How to calculate mode - Organize all the numbers in a ascending order and find the most frequently occurring value.
A situation where mode cannot be used - The mode cannot be used to find out the average cost of items that you have bought.
A situation where mode can be used - To find out if there is a certain fashion trend, for example to find out the amount of people wearing sneakers. If most people from the data collected wear sneakers, it means that there is a fashion trend of sneakers.