Ontario Mathematics Proficiency Practice Test

To determine the highest common factor (HCF) of 12 and 18, we start by identifying the factors of each number.

The factors of 12 are:

1, 2, 3, 4, 6, 12

The factors of 18 are:

1, 2, 3, 6, 9, 18

Next, we find the factors that are common to both sets. The common factors of 12 and 18 are:

1, 2, 3, 6

Among these common factors, the highest one is 6. This means that 6 is the largest number that divides both 12 and 18 without leaving a remainder. Therefore, the highest common factor of 12 and 18 is 6, making this the correct answer.

Recognizing the highest common factor is important for problems involving simplification of fractions, finding common denominators, and solving problems in number theory.