Easy Math Tricks: Multiplying by 4, 6, 9 and Beyond

There are many easy math tricks that you can teach your children or learn as an adult. I've written full articles on a few easy math tricks but there are some that are so easy that an explanation doesn't take an entire article. Some are so simple that it just takes a sentence or two. So I've compiled all the remaining multiplication tricks I know into this one article.

Easy Math Trick for Multiplying by 4

Multiplying by 4 might seem like a difficult task because it's not 2, 5, or 10, but it's pretty close to 2. What I mean by that is that 4 is 2 times itself. In order to find what something multiplied by 4 is all you have to do is multiply it by 2, two times and multiplying by 2 is pretty easy.

Example

4 times 3 is the same as multiplying 3 times 2 and then multiplying the answer by 2.

4 x 3 = 12

or

3 x 2 = 6 and 6 x 2 is 12

Let's try a harder example. What is 134 times 4?

Well 134 times 2 is 268 and 268 times 2 is 536. So 134 times 4 is 536.

Easy Math Trick for Multiplying by 6

Multiplying by 6 is not as easy as multiplying by 4 but sometimes you can use a similar method to come up with a multiplication of 6. 6 is 3 times 2 so to figure out a multiplication of 6 you can multiply by three and then multiply the answer by 2.

Example

6 times 3 is the same as multiplying 3 times 3 and then multiplying the answer by 2.

6 x 3 = 18

or

3 x 3 = 9 and 9 x 2 = 18

Let's try a harder example. What is 75 times 6?

75 times 6 will be the same as 75 times 3 and then the answer multiplied by 2. 75 times 3 is 225. 225 times 2 equals 450. So 75 times 6 is 450.

Easy Math Trick for Multiplying by 9

Multiplying by 9 looks like a daunting task but it is actually easily because the next number is the easiest number to multiply by, 10. To multiply a number by 9 all you have to do is multiply by 10 and then subtract the number you are multiplying by.

Example

If you are multiplying 9 times 2 then an easy way to figure it out is to multiply 2 times 10 and then subtract itself from the answer.

9 x 2 = 18

or

2 x 10 = 20 and 20 - 2 = 18

Let's try a harder example. What is 53 times 9?

53 times 9 would be 53 times 10 minus itself. So 53 times 10 is 530 and you subtract 53 from that to get 477. So 53 times 9 is 477.

Easy Math Trick for Multiplying by 13

To multiply by 13 it is easier to multiply the number by three and then multiply the number by 10 and then add the two numbers together.

Example

If you are multiplying 13 times 2 then you would multiply 3 times 2 and then 10 times 2. Then add the two answers.

13 x 2 = 26

or

3 x 2 = 6 and 10 x 2 = 20 and 6 + 20 = 26

Let's try a harder example: What is 24 times 13?

24 times 13 would be 24 times 3 and 24 times 10 added together. 24 times 3 would be 72 and 24 times 10 would be 240. 240 plus 72 would be 312. So 24 times 13 is 312.

Just about any other multiplication trick can be done in a similar way. When we multiplied by 13 we multiplied by 3 and them multiplied by 10 and then added the two numbers together. You can do that when you multiply by anything in the teens. Multiplying by 17 is the same as multiplying by 7, then multiplying by 10 and then adding the two numbers together.

To multiply by 9 we multiplied by 10 and then subtracted the original number. You can do this trick any time you multiply by a number that ends with nine. To multiply by 19 you can easily multiply by 20 and then subtract the original number once. Multiplying by 29 is the same as multiplying by 30 then subtracting the original number and so on.