Finding Least Common Denominators

What must you have to add and subtract fractions?

• Common numerators

• Different numerators

• Different denominators

• Common denominators

What is the least common denominator for 3 and 4?

• 6

• 4

• 3

• 12

What number could be a common denominator for these three fractions?
1/2   and   1/3   and   1/4

• 9

• 8

• 12

• 6

Add the following fractions by finding equivalent fractions with like denominators.

• 1/6

• 4/12

• 2/3

• 5/12

What is the least common denominator of 1/4 and 2/5?

• 5

• 25

• 10

• 20

What do you need to have when adding unlike fractions?

• common denominator

• common numerator

• common numerator and denominator

To find a common denominator you...

• add the denominators together

• skip count or list the multiples of each denominator until you find one they have in common

Why couldn't 12 be a common denominator for these two fractions?

• It could, you can just add 4 + 8 to get 12.

• 12 is a multiple of 4 but not a multiple of 8.

Which of these numbers could NOT be a common denominator for these two fractions?
2/4   and   3/8

• 32

• 12

• 8

• 24

Which of these numbers could NOT be a common denominator for these two fractions?
1/6   and   1/4

• 12

• 18

• 24

• 36