成人论坛

Watch: Multiplying three 1-digit numbers

Back to top

Multiplying three numbers

If you can multiply 2 numbers together, then this will help you multiply 3 numbers together!

How could you answer 3 x 8 x 2 using this array?

Group of cookies.

There are 3 rows of 8 cookies, so this array shows 3 x 8 = 24.

Now you have to multiply this by 2 to find the answer.

Two groups of 24 cookies.

24 x 2 = 48

Therefore:

3 x 8 x 2 = 48

This calculation was much easier, when we broke it down into stages.

You don鈥檛 need to always rely on arrays to help you solve multiplication problems involving three numbers.

Sometimes, it is easier and quicker to think, which numbers should I multiply first.

Back to top

Example 1

A girl thinking

What is 4 x 3 x 7?

Think which multiplication is easiest to solve first by using your times tables knowledge.

4 x 3 x 7 = 12 x 7

or

4 x 3 x 7 = 4 x 21

or

4 x 3 x 7 = 28 x 3

A girl thinking

It doesn't matter which one you choose to do first, you'll get the same answer at the end.

Solving 4 x 3 first to make 12 and then multiplying by 7 would probably be the easiest option to do in your head.

4 x 3 = 12

and then work out:

12 x 7 = 84

Sometimes it might not be easy to find the times tables link or use an array. This is when you could use short multiplication to help you.

Back to top

Example 2

What is 8 x 9 x 7?

Whichever numbers you chose to multiply first, you will always have a large 2-digit number multiplied by a 1-digit number.

Let鈥檚 solve 8 x 9 first.

8 x 9 = 72

Now let鈥檚 work out 72 x 7 using short multiplication:

Short multiplication of 72 x 7 = 504

Here's how you could solve this calculation using short multiplication:

  • Multiply 2 x 7 first to make 14.
  • Write the 4 in the ones column and carry the 1 into the tens column - you always need to make sure your place value is correct!
  • Then solve 70 x 7 = 490. Don鈥檛 forget about the extra ten: 490 + 10 = 500.

Therefore:

8 x 9 x 7 = 504

Back to top

Activity

Quiz

Back to top

Play our fun maths game Guardians: Defenders of Mathematica. game

Use your times tables and more maths skills to defeat monsters and reclaim the Kingdom of Mathematica

Play our fun maths game Guardians: Defenders of Mathematica
Back to top

More on Multiplying and dividing

Find out more by working through a topic