Math Background

Relating Multiplication and Division: When Students Ask

  • How do I know when to multiply and when to divide?
    When students solve word problems, have them identify words that help them decide which operation to use. Explain to students that they multiply when they want to find the number of objects in all. They divide when they want to find the number of equal groups or the number in each group.
  • Why should I memorize division facts? Can't I just use repeated subtraction?
    Let students answer this question themselves with a class demonstration. Have several volunteers use repeated subtraction to divide while another volunteer times them. Students will see that using repeated subtraction can take a lot of time.
  • How does knowing how to multiply help me to divide?
    Point out to students that multiplying and dividing are inverse, or opposite, operations. For example, if they know that 7 x 3 = 21, they also know that 21 ÷ 7 = 3.
  • Why should I bother learning division, especially if I have a calculator?
    Explain to students that they will use division in situations in which a calculator may not be on hand, such as when they are shopping or at sporting events.

Houghton Mifflin Math Grade 3