A cluster in math is when data is clustered or assembled around one particular value. An example of a cluster would be the values 2, 8, 9, 9.5, 10, 11 and 14, in which there is a cluster around the number 9.
A cluster in mathematics is often used in data with a classification, which is called data clustering. When using data clustering, a person takes a group of numbers that surrounds a single number and creates a data set. An example of data clustering would be taking 6 people who ran a 100 meter sprint and analyzing their times in seconds. If the times were 39, 34, 35, 34, 33 and 27 seconds, then the data would be clustered around the 34 second mark.
Understanding clusters and data clustering can help young children and adults estimate sums in equations. This is called cluster estimation, and many people use it every day when buying items from the store without being aware of it. An example of cluster estimation would be estimating the sum of 399, 346 and 411. It's possible to determine the sum with a calculator; however, to do this quickly and without much thought, a person can use the cluster estimation method. The numbers 399, 346 and 411 all cluster around the number 400. A person would substitute the numbers for 400 to make the equation become 400 + 400 + 400. The person could solve this equation without a calculator, and the cluster estimation would be 1,200.