Which of the following is NOT a factor of 12?

A factor of a number is defined as any integer that can be multiplied by another integer to produce that number. For the number 12, we can identify its factors by looking for integers that fit this definition.

The factors of 12 are:

• 1 (1 × 12 = 12)

• 2 (2 × 6 = 12)

• 3 (3 × 4 = 12)

• 4 (4 × 3 = 12)

• 6 (6 × 2 = 12)

• 12 (12 × 1 = 12)

Among the choices provided, the integers 1, 3, and 12 are factors of 12 because they can be paired with other positive integers to equal 12. However, the number 5 cannot be paired with any integer to achieve a product of 12, making it not a factor of 12. Therefore, identifying 5 as the option that is not a factor aligns accurately with the definition of what factors are.