Example of adding fractions with unlike denominators word problem | Pre-Algebra | Khan Academy

TL;DR

Cindy and Michael have 2/5 of a gallon of red paint and 1/2 a gallon of yellow paint. When mixed together, they have a total of 9/10 of a gallon, which is less than the 1 gallon they need.

Transcript

Cindy and Michael need 1 gallon of orange paint for the giant cardboard pumpkin they are making for Halloween. Cindy has 2/5 of a gallon of red paint. Michael has got 1/2 a gallon of yellow paint. If they mix their paints together, will they have the 1 gallon they need? So let's think about that. We're going to add the 2/5 of a gallon of red paint,... Read More

Key Insights

• 🪡 Fractions with different denominators need a common denominator to be added.
• ❓ 2/5 of a gallon is equivalent to 4/10 or 40 tenths, and 1/2 a gallon is equivalent to 5/10 or 50 tenths.
• ✖️ To convert fifths to tenths, each fifth is multiplied by 2. To convert halves to tenths, each half is multiplied by 5.
• 🪜 Adding 4/10 and 5/10 results in a total of 9/10 or 90 tenths.

Questions & Answers

Q: How much red paint does Cindy have?

Cindy has 2/5 of a gallon of red paint, which is equivalent to 4/10 or 40 tenths of a gallon.

Q: How much yellow paint does Michael have?

Michael has 1/2 a gallon of yellow paint, which is equivalent to 5/10 or 50 tenths of a gallon.

Q: What is the common denominator used to add the fractions?

The common denominator used to add the fractions is 10, as it is the smallest multiple of both 5 and 2.

Q: How much paint do they have when mixed together?

When the red and yellow paints are mixed together, they have a total of 9/10 of a gallon, which is equivalent to 90 tenths.

Summary & Key Takeaways

• Cindy has 2/5 of a gallon of red paint and Michael has 1/2 a gallon of yellow paint.

• To add the fractions, a common denominator of 10 is used.

• When the paints are mixed, they have a total of 9/10 of a gallon, which is less than the 1 gallon they need.