Multiplication
Multiplying in your head
Here are some tips for multiplying in your head.
- Try 7 x 6
Use your knowlege of times tables to recall the multiplication fact for 7 x 6 to get the answer 42. - 12 x 7
Remember that 12 is 2 x 6, so 12 x 7 can also be expressed as:
2 x 6 x 7
(12) x 7
Recall from your times tables that 6 x 7 = 42
So times 42 by the remaining 2 to get the answer: 42 x 2 = 84 - 35 x 8
Because 8 is 2 x 2 x 2, when you work out 35 x 8, you can do it like this:
35 x 2 x 2 x 2
= 70 x 2 x 2
= 140 x 2
= 280 - To multiply a number by 10, move the digits one place to the left, adding a zero if necessary.
58 x 10 = 580
- To multiply a number by 100, move the digits two places to the left, adding zeros if necessary.
58 x 100 = 5800
- To multiply by numbers such as 20 or 300, multiply by the 2 or 3 first and then by the 10 or 100.
33 x 20
= 33 x 2 x 10
= 66 x 10
= 660
22 x 300
= 22 x 3 x 100
= 66 x 100
= 6600
Grid Method
When you use the grid method, you break up the number into hundreds, tens and units. Multiply each separately and then add the answers together.
For example, 327 x 6
For example, 327 x 6
For example, 246 x 3
For example, 248 x 58
Vertical Method
When using the vertical method, line up the units, tens and hundreds underneath each other and then multiply each digit, starting with the units.
Example 1246 x 3
Start by multiplying the 3 by the 6 to give 18.
Example 1246 x 3
Start by multiplying the 3 by the 6 to give 18.
Then multiply the 3 by the 4 to give 12. Add the 1 carried over to give 13.
Then multiply the 3 by the 2 to give 6. Add the 1 carried over to give 7.
So the answer to 246 x 3 is 738.
Example 238 x 13
If you are multiplying by a number over 10, for example 38 x 13, you use the same method as above but break it down into 2 parts, 38 x 3 and 38 x 10, and then add the two answers together:
Example 238 x 13
If you are multiplying by a number over 10, for example 38 x 13, you use the same method as above but break it down into 2 parts, 38 x 3 and 38 x 10, and then add the two answers together:
Useful Tips
- Estimate first and check afterwards.
- Multiplication and division are opposites.
- The order in which you multiply numbers doesn't matter.