**Square of numbers ending with 5:-**

** **

Formula for calculating square ending with 5 is easy.

85

x

85

————-

7225

**Steps**

• First, place 25 (in any square ending with 5) on the right hand side.

• Add 1 to the other number. In this example, its 8 and hence 8+1=9

• Multiply 9 to the previous number – i.e. 9*8=72

• Our answer is 7225.

**Multiply any two numbers from 11 to 20 in your head:-**

Take 15 x 13 for example… Place the larger no. first in your mind and then do something like this.

Take the larger no on the top and the second digit of the smaller no. in the bottom.

15

3

The rest is quite simple. Add 15+3 = 18 . Then multiply it by 10. In this example – 18 x 10 = 180 …

Now multiply the second digit of both the no.s (ie; 5 x 3 = 15) Now add 180 + 15. Here is the answer 180 + 15 = 195 . Think over it. This is a simple trick. It will help you a lot.

**Multiplying by 15 :-**

What is 15? Remember, 15 is 10 + half of 10.

So if you to have to multiply any number with 15, this trick or simple math rule will help improve your arithmetic computation speed. Say you have to find the product of 67 with 15.

- Write 0 at the end of the number. Here we have 67, so adding 10 would make it 670
- Divide this by 2. So we have 335
- Add up the 2 numbers i.e. 335+670 = 1005

You must be logged in to post a comment.