2- and 3-Digit Multiplication

Lesson Plan - Get It!

Audio:

Multiplying multi-digit numbers is similar to multiplying single digit numbers, except there are a few more steps involved.

The following video will walk you through the steps of multiplying a multi-digit number by another multi-digit number. As you watch Math Antics - Multi-Digit Multiplication Pt 2, write down the answers to the following questions:

• How is multiplying a single-digit number on the bottom different from having a multi-digit number on the bottom?
• What important step needs to be remembered when moving to the second line of multiplication?

Discuss the questions with a parent or teacher after you watch the video:

When multiplying a two- or three-digit number by a two-digit number, start multiplying in the ones place, then move to the tens place.

Look at how to set up and solve the problem from the beginning of the lesson.

The bakery sells 21 donuts in a box.

• If Sandra buys 12 boxes of donuts, how many donuts will she have?

The multiplication problem is 21 x 12 because each box contains 21 donuts. Instead of adding 21 to itself 12 times, we multiply. The order of the numbers in multiplication doesn’t matter.

Step 1 Write the problem and line up the digits.

Step 2 Multiply the digit in the ones place of the bottom number by both digits in the top number.

Step 3 Move to the tens place to begin multiplying that digit by the digits in the top numbers. Since you are now multiplying numbers in the tens place, you will need to add a place holder of zero (0) to represent this. 

Step 4 Multiply the number in the tens place of the bottom number by both digits of the top number. Notice how the numbers in the answer are moved down a row and shifted over to the left because of the place holder zero.

Step 5 Add up the two products below the original problem. In this problem, add 44 + 220 =, which is 264. There are 264 donuts in 12 boxes.

When multiplying larger numbers, such as a three-digit number by a two-digit number, the steps are similar.

Example: 526 x 52 =

Step 1 Write the digits so that the ones, tens, and hundreds spots are lined up. Since the number 52 does not have a digit in the hundreds place, it is left blank. Although the numbers can be written in any order, the number with the greater number of digits is usually written on the top.

Step 2 Multiply the bottom digit in the ones place by each digit in the top number. If a number is larger than 9 in any place value spot, you need to regroup.

Step 3 Multiply the bottom digit in the tens place by each digit in the top number. Don’t forget to add the place holder zero!

Step 4 Add the products together to get the final answer: 526 x 52 = 27,352.

Discuss with a parent or teacher:

• When setting up a multiplication problem, which number is written on the top?
• How do you know if you need to regroup when multiplying?

In the Got It? section, you will practice multiplying two- and three-digit numbers with interactive practice.