Adding and Subtracting Fractions Unlike Denominators Using Models

Find the LCD for 1/3 and 2/9

Which shows a way to solve 3/7 + 2/5

• _{Add the numerators first, then add the denominators.}

• Find the LCD for 7 and 5, then make equivalent fractions and then subtract

• Find the LCD for 7 and 5, then make equivalent fractions and then add

• Find the LCD for 7 and 5, then multiply both numerators by 5.

What is the first step in finding the Least common Denominator for two fractions?

• List all of the multiples of each numerator

• Multiply the numerators together

• Add the denominators

• List the first few multiples of each denominator

What must you do first in order to add or subtract fractions with unlike denominators?

• add the numerators

• add the denominators

• find a common denominator

• find a common numerator

When the denominators are not the same, I must find a...

• common numerator

• common denominator

• equivalent fraction

• mixed number

When adding or subtracting fractions, I NEVER add or subtract the...

• numerators

• denominators

• mixed numbers

• equivalent fractions

Once I have completed adding or subtracting fractions, I should always ____________ if possible.

• make equivalent fractions

• add again

• simplify

• multiply

Solve.

• 5/8

• 23/40

• 21/40

• 1/2