 Multiplying with a tens number and a number to 100

# Multiplying with a tens number and a number to 100

Students learn to multiply with a tens number and a number to 100.

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## General

Students learn to multiply with a tens number and a random number to 100.

## Standards

CCSS.Math.Content.4.NBT.B.5

## Learning objective

Students will be able to multiply with a tens number and a random number to 100.

## Introduction

Show several multiplication problems on the interactive whiteboard. The students solve these and then drag away the cover to show what the correct answers are. Then you solve a few problems in story problem form.

## Instruction

Show the problem on the interactive whiteboard and ask the students how they would solve it. Then show that you can solve this problem in steps by splitting it into two problems. Solve these two problems and then add the answers together. After that, show some other possible methods to solve the problem. You can swap the numbers, because sometimes it is easier that way, or you first calculate the problem without and 0 and then put the 0 at the end of the answer. Have the students solve a few problems and ask how they solved them. Finally you show how you can solve a story problem. You have the students determine what type of problem it is, which numbers you need and to make the problem and solve it. Then have the students solve the next few story problems on their own.

Check whether the students can multiply with a tens number and a number to 100 with the following question:
- How do you solve the problem jij 64 × 80?

## Quiz

Students test their understanding of multiplying with a tens number and a number to 100 through 10 exercises. For some of these they get a choice between possible answers, some they must come up with an answer on their own, and others are word problems.

## Closing

You discuss once again with the students that it is important to be able to multiply with a tens number and a random number to 100, because that is how you can solve multiplication problems with large numbers. As a closing activity have the students work in pairs. They come up with a problem together and solve it individually. Next they discuss with each other how they calculated the answer to the problem and see if they have the same answer.

## Teaching tips

Have students that have difficulty with multiplying with a tens number and a number to 100 first practice with multiplication problems which consist of one number between 1 and 9. The other number is a random number to 100. Next you show them the same problem, but put a 0 after the number that is between 1 and 9. Can the students solve this problem in steps too?

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