Fractions with Unlike Denominators

What is the least common denominator of 1/9 and 2/3?

• 6

• 3

• 9

• 21

Answer explanation

The least common denominator of 1/9 and 2/3 is 9, as it is the smallest multiple of both denominators, 9 and 3.

Find the lowest common denominator of these fractions: 2/7 and 2/21

• 7

• 21

• 18

• 147

Answer explanation

The lowest common denominator of 2/7 and 2/21 is 21, as it is the least common multiple of the denominators.

Find the least common denominator of 1/5 and 2/10.

• 10

• 5

• 50

• 15

Answer explanation

The least common denominator of 1/5 and 2/10 is 10, as it is the smallest multiple of both denominators.

Which of these numbers could NOT be a common denominator for 1/6 and 5/18?

• 6

• 18

• 36

• 108

Answer explanation

The number 6 could NOT be a common denominator because it is already the denominator of 1/6, making it unnecessary for 5/18.

What do you need to have when adding unlike fractions?

• common denominator

• common numerator

• common numerator and denominator

Answer explanation

When adding unlike fractions, you need to have a common denominator in order to add the fractions together.

Is this a correct answer?

• Yes, the student correctly added.

• No, you cannot add unlike denominators

• No, 5 + 7 is not 12

• No, 2 + 3 is not 5

Answer explanation

No, you cannot add unlike denominators because they represent different parts of a whole and cannot be directly added together.

• 2

• 9

• 36

• 18

Answer explanation

The least common denominator of 2 and 9 is 18, as it is the smallest multiple that both 2 and 9 can divide into evenly.

• 4

• 40

• 20

• 5

Answer explanation

The least common denominator of 20 and 4 is 20, so the correct answer is 20.

• 3

• 27

• 18

• 9

Answer explanation

The least common denominator of 9 and 3 is 9, as it is the smallest multiple that both denominators share. Therefore, the correct answer is 9.

• 45

• 9

• 5

• 90

Answer explanation

The least common denominator of 5 and 9 is 45. Therefore, the correct answer is 45.