Addition and Subtraction of Fractions of Unlike Denominators

What is the least common denominator for this problem?

• 6

• 12

• 18

• 24

What is the least common denominator for this problem?

• 18

• 9

• 24

• 12

What is the least common denominator for this problem?

• 24

• 18

• 32

• 16

What is the least common denominator for this problem?

• 18

• 9

• 24

• 12

What is the sum of these fractions in lowest terms?

• 4/5

• 3/20

• 17/20

• 4/20

What is the least common denominator for this problem?

• 12

• 24

• 36

• 16

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 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

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 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.