Multiplying by 0 or 1
Background Information & Activities

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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.

See more lesson plans and resources: BrainPOP Educators.

Multiplying by 0 or 1 Teacher Activities

© 1999-2012 BrainPOP. All rights reserved.

Bean Bags

Divide students into small groups and provide each group with clear plastic baggies and small counters, such as blocks or dried beans. Then write multiplication sentences with 0 or 1 on the board, such as 3 x 1 = __ or 10 x 1 = __. Have students use the baggies and beans to solve the number sentences. Then have one group member put a different number of beans into the baggies and challenge the other group members to come up with the number sentence.

Addition/Multiplication

On index cards, write a multiplication sentence, such as 3 x 0 = __. On another card, write its related addition sentence, such as 0 + 0 + 0 = __. Give an index card to each student and have everyone mingle around the room to find their related partner. Then have the partners solve the number sentences together. You can repeat this activity several times so children get an opportunity to solve different sentences. You may wish to have students make more pairs of cards by writing addition and multiplication sentences they create on their own.

Multiplying by 0 or 1 Family Activities

© 1999-2012 BrainPOP. All rights reserved.

Missing

Explore algebraic concepts with your child. Write a multiplication sentence such as 9 x ___ = 0. Then have your child find the missing number. Then write a sentence such as 4 ___ 1 = 4. What's the missing operation? Next, challenge your child to write a sentence for you to solve. He or she may want to write out the complete number sentence first in pencil and then erase a number or the operation sign. When you solve, you may want to "make a mistake" and have your child explain the correct answer.

Zero Hero

Help your child understand the differences between adding 0, subtracting 0, or multiplying by 0. Provide a variety of number sentences, such as 2 + 0 = __, 2 – 0 = __, and 2 x 0 = __, and have your child solve. You may want to do this together using counters. Consider using small numbers at first so your child can practice adding, subtracting, and multiplying, and then later use four-digit numbers so your child can see how the rule still applies to large numbers.