# Multiplication Tips and Tricks

## Some Tips and Tricks

Here are some tips and tricks to help you with multiplication.

*Everyone thinks differently, so just ignore any tricks that don't make sense to you.*

First of all: **Memory** is your best friend! With the whole table in your memory you will just **know** that 3×5=15, 6×8=48 etc. Memory is fast, too.

Math Trainer - Multiplication is designed to

help you remember your tables.

## The Best Trick

**Every multiplication has a twin, which may be easier to remember. **

**For example if you forget 8×2, you might remember 2×8=16. This way, you only have to remember half the table. **

## Tricks by Number

2

add the number to itself (in other words, double it)

Example 2×9 = 9+9 = 18

4

double, then double again

Example 4×9: double 9 is 18, double 18 is **36**

5

Cut in half, then times 10

Example: 5x6: Cut 6 in half to get 3, then times 10 for **30**

Or times 10 then cut in half

Example: 5x9: 9 times 10 is 90, then cut in half for **45**

Also the last digit goes 5, 0, 5, 0, ... like this: **5**, 1**0**, 1**5**, 2**0**, ...

6

when you multiply 6 by an even number, they both end in the same digit.

Examples: 6×**2**=1**2**, 6×**4**=2**4**, 6×**6**=3**6**, etc

7×8

Think "5,6,7,8": **56=7×8**

8

Double, double, double!

Example: 8×6: double 6 is 12, double 12 is 24, double 24 is **48**

9

is 10× the number minus the number.

Example: 9×6 = 10×**6**−**6** = 60−6 = 54

the ones digit goes 9, 8, 7, 6, ...: **9**, 1**8**, 2**7**, 3**6**, 4**5**, ...

the tens digit goes 0, 1, 2, 3, ...: 9, **1**8, **2**7, **3**6, **4**5, ...

subtract one to get the tens digit, and the tens and ones digit together make 9

Example:
9×**5**: tens digit is **4**, 4 and **5** make 9, so **45**

Example:
9×**8**: tens digit is **7**, 7 and **2** make 9, so **72**

your hands can help! Example: to multiply 9 by 8, hold your 8th finger down, and count "7" and "2",
the answer is **72**

10

put a zero after it

Example: 10×**2** = **20**

11

up to 11x9: just repeat the digit. Example: 11x**4** = **44**

for 11×10 to 11×18: write the sum of the digits between the digits

Example: 11×15 = 1*(1+5)*5 = 165*
* Note: this works for any two-digit number, but when the
sum of the digits is more than 9, we need to"carry the one".
Example: 11×75 = 7

*(7+5)*5 =

**7**

*(*5 =

**1**2)**8**25.

12

is 10× plus 2×

Example: 12×**4** = **40**+**8** = 48

15

multiply by 10, then add half again

Example: 15×**4** = **40**+**20** = 60

Example: 15×**9** = **90**+**45** = 135

20

multiply by 10, then double

Example: 20×**4** = **40**+**40** = 80

Example: 20×**7** = **70**+**70** = 140

## Remembering Squares Can Help

This may not work for you, but it worked for me. I like remembering the squares (where you multiply a number by itself):

And this gives us one more trick. When the numbers we are multiplying are separated by 2 (example 7 and 5), then multiply the number in the middle by itself and subtract one. See this:

5×5 = 25 is just one bigger than 6×4 = 24 |

6×6 = 36 is just one bigger than 7×5 = 35 |

7×7 = 49 is just one bigger than 8×6 = 48 |

8×8 = 64 is just one bigger than 9×7 = 63 |

etc ... |