Math Background

Addition and Subtraction of Fractions: When Students Ask

  • Why should I bother learning this? This is an excellent opportunity to generate a class discussion about the fact that not all numbers are whole numbers. Too often, students are under the assumption that numbers in the real world are always whole numbers. Use this opportunity to talk about activities such as cooking that can involve the addition of fractions. Another example is distances, such as tenths of a mile.
  • Why don't you add the denominators when adding and subtracting fractions? When students ask this type of question, use a manipulative that demonstrates the fact that when adding fourths, you will get fourths. Have your students use paper fraction kits to model this operation.
  • Should I write the fraction one-half as 1/2 or one-half?It is likely that students will see both written variations in their educational careers. Although 1/2 is commonly accepted, one-half usually generates much less confusion for students. When students see 1/2 + 5, they may be tempted to add the 2 + 5 first. Do your best to be consistent. It is a good idea to let students know that they may encounter both variations later in their mathematical endeavors.

Houghton Mifflin Math Grade 3