Module 1 · Numbers and number sets · Lesson 2 of 39
Identity numbers
0 is the identity for addition and 1 is the identity for multiplication.
In this lesson · about 6 minutes
- Name the identity numbers for addition and multiplication
- Use them to simplify quickly
An identity number doesn't change the "identity" of the number it works on.
- The identity for addition is 0: 17 + 0 = 17.
- The identity for multiplication is 1: 4 × 1 = 4.
Adding nothing leaves what you had, and taking one copy of something leaves it as it is. This idea comes back later when we multiply a fraction by 22 or 55 (both equal to 1) to rewrite it without changing its value.
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