Subtracting Fractions with Unlike Denominators

Matt and Mr. J demonstrate how to subtract fractions with unlike denominators. They start with the problem two-thirds minus two-fifths and explain the need for a common denominator. The least common multiple of the denominators, three and five, is found to be fifteen. The fractions are then renamed with this common denominator, and the subtraction is performed. The result, four-fifteenths, is already in its simplest form. The video concludes with a quick review and a suggestion to check the description for a more detailed explanation.

Why do we need a common denominator when subtracting fractions?

• To make the numerators equal

• To ensure the fractions have the same base for subtraction

• To simplify the fractions

• To convert fractions to decimals

What is the least common multiple of 3 and 5?

• 10

• 20

• 15

• 30

How do you convert two-thirds to have a denominator of 15?

• Subtract 3 from the denominator

• Add 5 to the numerator

• Multiply both numerator and denominator by 5

• Multiply both numerator and denominator by 3

What is the result of subtracting 10/15 and 6/15?

• 8/15

• 2/15

• 4/15

• 6/15

What is the simplest form of the fraction 4/15?

• 3/5

• 4/15

• 1/3

• 2/5