Addition and Subtraction of Fractions Unlike Denominators

When you add or subtract fractions with unlike denominators you..

• Add both the numerators and denominators

• Change the denominator by picking a random number then divide

• Find the least common multiple of both denominators

• none of these are true

What must you have to add and subtract fractions?

• Common numerators

• Different numerators

• Different denominators

• Common denominators

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

What is the first step in solving this problem? 
⅘ + ½ =

• Add the top parts of the fraction

• Rewrite the fractions in the simplest form. 

• Find a common denominator. 

• Make each fraction into an improper faction. 

What is the the next step to finding this answer?

• Add the numerators (1+1=2)

• Multiply 12 X 1 for both fractions to find a new numerator
  

• Multiply to find each new numerator by the multiple used to get 12. (3 X1) (4 X 1)

• This is a mistake, you don't need to convert to twelfths

What is the best Common Denominator for the Given Problem?

• 48

• 24

Following the integer rules, would you add or subtract the fractions?

• add, the answer would be positive

• add, the answer would be negative

• subtract, the answer will be positive

• subtract the answer will be negative

3/10 - (-1/4)

• 11/20

• 3/15

• 15/20

• 3/4

(-7/8) + 1/3

• -13/24

• -11/24

• 11/12

• 12/24

(-1/15) + (-3/5)

• -2/3

• 2/3

• 1/4

• -1/4