Related facts are basic mathematical expressions made up of three numbers. Related facts are often taught as part of early math alongside fact families and addition, subtraction, multiplication, and division facts.
Related facts can be used to teach or reinforce a student's understanding of the relationships between the operations of addition and subtraction, and multiplication and divison.
Addition and subtraction
Addition and subtraction are inverse operations. If you add one number, then subtract the same number, they cancel each other out and there is no effect on the expression.
Below are the related addition and subtraction facts using the numbers 2 and 3:
|2 + 3||=||5||3 + 2||=||5|
|5 - 3||=||2||5 - 2||=||3|
The same related facts can be written for any addition or subtraction problem. If we are given one of the facts, we can write three other facts using the same three numbers and addition or subtraction. Each of the sets of expressions (ex. 2 + 3 = 5 ; 3 + 2 = 5) is referred to as a fact family.
Multiplication and division
Multiplication and division, like addition and subtraction, are inverse operations. They "undo" each other. Multiplying by a number and then dividing by that same number does not change an expression.
Below are the related multiplication and division facts using 2 and 4 as factors:
|2 × 4||=||8||4 × 2||=||8|
|8 ÷ 4||=||2||8 ÷ 2||=||4|
Like addition and subtraction, each of the sets of three numbers in the multiplication and division facts above makes up a fact family, which can be used to write a total of four related facts.
Remembering related facts, particularly for multiplication and division, can help reduce the number of basic facts a student truly has to memorize. As long as the student knows the solution to a multiplication problem involving two numbers, they can also know the relationship between those numbers and division.