add/sub fractions

What must you have to add and subtract fractions?

• Common numerators
• Different numerators
• Different denominators
• Common denominators

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

• 9
• 8
• 12
• 6

What number could be a common denominator for these two fractions?
1/5   and   5/6?

• 30
• 11
• 6
• 5

Reduce if needed.

• 11/10
• 5/6
• 1  1/10
• 3  3/7

• 5 7/12
• 4 7/12
• 5 5/12
• 4 5/12

• 1  7/8
• 2  1/8
• 3
• 6   3/8

3/4 + 2/8 = 

• 1
• 5/12
• 6/32
• 5/8

5/7 + 1/28 = 

• 6/35
• 12/196
• 21/28
• 1

6/7 - 2/3 =

• 32/21
• 4/21
• 1 3/21
• 7/21

5/8 - 1/2 

• 9/8
• 1 1/8
• 1/8
• 3/8