Add and Subtract Positive Rational Number

Hey everyone,

I think this might be one of those posts that I continue to add onto as the time progresses. This is taught in fifth grade but I see sixth graders struggle with this and even seventh grade students.

For instance we might see something like this.

Michael bought 2 2/3 pounds of bananas from the store. He used 1.25 pounds of bananas to bake muffins. How many pounds of bananas does Michael have left?

So here we have students either having to convert the decimal to a fraction and solve or the fraction to a decimal and solve. Not only are they converting this then they need to have the same denominator.

I talked about adding and subtracting unlike denominators in my last post.

So just to get this started I am going to lay out the academic vocabulary students need to know and understand. Then some of the misconceptions and ways to address those misconceptions.

Academic Vocabulary

  • Benchmark fractions: Fractions that are easy to round to and add and subtract with
  • Common denominators: When two fractions have the same denominator
  • Decimals: numbers between whole numbers with one or more digits to the right of the decimal point that represent part of one whole
  • Estimate: An approximate number close to the actual value
  • Fraction: A number that represents a part of a whole
  • Greatest common factor: The greatest common factor shared by two or more numbers
  • Equivalent fractions: Fractions that name the same part of a whole region, set, or distance on a number line
  • Simplest form: The form of a fraction when the numerator and denominator have the number 1 as the greatest common factor.

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