This grade 3 multiply tens lesson explains multiplying by multiples of 10 in one printable page, with definitions, a method and a worked example.
To multiply a one-digit number by a multiple of 10, think of the multiple of 10 as tens. For 9 × 80, find 9 × 8 = 72, so you have 72 tens, and 72 tens is 720. Multiply the basic fact, then write the extra zero for the ten in each group.
Grade 3 Multiply Tens Lesson: key facts
- A multiple of 10, like 40, is a number of tens: 40 is 4 tens.
- Multiply the basic fact first: 6 x 4 = 24, so 6 x 40 = 240.
- The product is the number of tens written as a regular number.
- Skip counting by tens and drawing arrays can check the product.
What does it mean to multiply by a multiple of 10?
A multiple of 10 is a number you get by counting by tens: 10, 20, 30, 40, and so on up to 90. A number such as 30 is 3 tens. So \(3 \times 20\) means 3 groups of 2 tens, and each ten is worth 10.
There are 6 rods in all, so there are 6 tens. 6 tens is 60. That means \(3 \times 20 = 60\).
A multiple of 10 is a product of 10 and a whole number, such as 20, 50, or 80. A basic fact is a multiplication fact with factors from 1 to 10, such as \(6 \times 4 = 24\). A product is the answer to a multiplication problem.
How do you use a basic fact to multiply by 10s?
Treat the tens as the unit you are counting. Here is the method for \(9 \times 80\).
- Write 80 as 8 tens.
- Multiply the basic fact: \(9 \times 8 = 72\). So 9 groups of 8 tens is 72 tens.
- Say 72 tens as a number: 72 tens is 720.
So \(9 \times 80 = 720\). The product is the basic fact with one zero written after it.
| Basic fact | Think | Product |
|---|---|---|
| \(6 \times 4 = 24\) | \(6 \times 40\) is 24 tens | \(240\) |
| \(6 \times 5 = 30\) | \(6 \times 50\) is 30 tens | \(300\) |
| \(6 \times 7 = 42\) | \(6 \times 70\) is 42 tens | \(420\) |
Why does skip counting by tens work?
Each group has the same number of tens. Jumping 5 times by 30 lands on 30, 60, 90, 120, 150. That matches \(5 \times 30 = 150\).
How can you see the product in an array?
Picture a grid where every square is worth 10. If there are 4 rows with 7 squares in each row, there are \(4 \times 7 = 28\) squares. Each square is worth 10, so the total is \(28 \times 10 = 280\), which equals \(4 \times 70\).
Watch out: do not forget the tens. \(6 \times 40\) is 240, not 24. Always say the answer as tens first, then change it to a number.
Multiplying by Multiples of 10: frequently asked questions
What is a multiple of 10?
A multiple of 10 is a number you reach by counting by tens, such as 10, 20, 30, up to 90 and beyond. Every multiple of 10 ends in a zero.
Why does 9 x 80 equal 720?
80 is 8 tens, and 9 groups of 8 tens is 72 tens. 72 tens is 720. The basic fact 9 x 8 = 72 tells you the digits.
Is there a shortcut for multiplying by 10s?
Yes. Multiply the basic fact and write one zero after the product. The zero stands for the ten in each group, so 7 x 30 is 7 x 3 = 21, then 210.
What if the basic fact ends in zero, like 5 x 60?
5 x 6 = 30 is the basic fact, which has a zero already. 30 tens is 300, so the product has two zeros. Think of it as 30 tens.
How can you check a product like 4 x 70 = 280?
Skip count by 70 four times : 70, 140, 210, 280. You can also estimate, because 4 x 70 is close to 4 x 100 = 400 and a little less.
How to use this grade 3 multiply tens lesson
Use this grade 3 multiply tens lesson before the worksheet, then check what you learned with the quiz.
See every chapter on the Grade 3 math page.