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Missing Quantities in Multiplication & Division Problems: Lesson for Kids

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  • 0:04 Missing Quantities in…
  • 1:00 Multiplication Problems
  • 1:36 Division Problems
  • 2:09 Multi-Step Problems
  • 2:53 Lesson Summary
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Lesson Transcript
Instructor: Lynn Knott

Lynn has taught 1st and 3rd grade and has a master's degree in Educational Leadership.

Missing quantities in math problems can take one or more steps to find. In this lesson, you'll learn how to solve multiplication and division problems with missing quantities and how to complete multi-step problems.

Missing Quantities in Math Problems

Your teacher tells your class she wants to play a game. She writes three words on the board and tells you to do your best to remember them. The words are ''pencil,'' ''book,'' and ''horse.'' She then tells the class to close their eyes while she erases one of the words. When you open your eyes, you see only two of the words still on the board: pencil and book. The other word has been erased.

Your teacher asks your class for the missing word. Everyone says ''horse.'' How did they know this was the correct answer? By seeing which other words were left on the board!

This is the same way we handle missing quantities in multiplication and division equations. We use the information we have to solve for the missing quantity. A missing quantity is just the part of the equation that's not there; it's a mystery number. A missing quantity can be the first, second, or last number in an equation.

Multiplication Problems

Multiplication is just adding the same number over and over until you reach the total you want. You may already know 2 x 4 = 8. If we take away one of the numbers, would the problem change? Let's take a look.

Example of a multiplication problem with a missing quantity
Image of a missing quantity multiplication problem.

The way we solve for a missing quantity in a math problem is to try a number in the missing spot and see if the problem stays the same. If it changes the equation, we try another number.

We could also solve for the missing quantity by dividing. For example: 8 / 2 = 4 and 8 / 4 = 2.

Division Problems

Division is just backwards multiplication. We start with a bigger number and break it into pieces. Let's look at the equation 8 / 2 = 4. We know the problem stays the same even if we remove a number.

Example of a division problem with a missing quantity
Image of a division problem with a missing quantity.

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