Multiplying by 0 or 1 Background Information for Teachers, Parents and Caregivers

This page provides information to support educators and families in teaching K-3 students about multiplying by 0 or 1. It is designed to complement the Multiplying by 0 or 1 topic page on BrainPOP Jr.

This movie will explore multiplying by 0 and 1. These concepts can be confusing for some children, so we recommend doing plenty of hands-on activities. You may want to solve number sentences together using counters and creating arrays, and watch the Arrays movie to build background knowledge.

Remind children that when they multiply, they put equal groups together to find the total. Write the number sentence 3 + 3 + 3 + 3 = on the board or on a piece of paper. Then use counters and cups to solve the number sentence. Place 3 counters into each of 4 cups and have children count or add the counters to find the sum: 3 + 3 + 3 + 3 = 12. Explain that multiplying is much easier than adding the same number over and over again: 3 x 4 = 12. The multiplication sentence shows that you are adding the number 3 a total of 4 times. Use cups and counters to repeat the same activity with other number sentences, such as 1 + 1 + 1 + 1 + 1 + 1 + 1 = and 5 + 5 + 5 =.

Then show 4 cups without counters. How many counters are there? Explain that while there are 4 cups, they are all empty. There are 0 counters in each cup. You can use the number sentence 0 + 0 + 0 + 0 = to show how you are adding 0 counters a total of 4 times. Explain that since there are 0 counters in each cup, there are 0 counters in all. Then write the following multiplication sentence: 4 x 0 = 0. Repeat the activity again, this time with 10 cups without any counters. What multiplication sentence shows the number of counters? 10 x 0 = 0. Help them understand that they could have a million or trillion cups, but if the cups have nothing in them, they are left with 0. Explain that if a number is multiplied by 0, the answer is always 0.

Now show 4 cups with 1 counter in each cup. What is the total number of counters? You can use the number sentence 1 + 1 + 1 + 1 = 4 to show how you are adding 1 counter for a total of 4 times. But, an easier way to solve is by using multiplication: 1 x 4 = 4. Repeat the activity again using 12 cups with 1 counter in each cup. Guide children to write the multiplication sentence 12 x 1 = 12. Explain that if a number is multiplied by 1, the answer is always that same number. So if you have 10,000 cups and each has 1 counter, then you have 10,000 counters.

Provide different multiplication sentences with 0 or 1 and have children use cups and counters to find the answer. Then create a set of cups with 0 or 1 counter in each cup and have children write a multiplication sentence that describes the set. How is multiplying easier than adding the same number over and over again? Discuss together. Have children continue to practice solving multiplication sentences with 0 or 1. Then extend the concepts by having them solve multiplication sentences with very large numbers.