# Tips for calculations

In mathematics, there are some calculations that are very laborious, right? For Just Mathematics decided to make your life easier by giving you some useful calculation tips that can be used in certain situations. Enjoy and speed up your calculations!

## TIP 1: Multiply a Number by 10

Just move the comma one decimal place to the right.
Example 1: 16x10 = 160
Example 2: 15.567 x 10 = 155.67

## TIP 2: Multiply a Number by 10no

Just move comma n decimal places to the right.
Example 1: 16x103 = 16000
Example 2: 15.567 x 104 = 155670

So if we want to do the following multiplication: 12 x 100. We know that 100 = 102, then:
12x100 = 12x102 = 1200.

## TIP 3: Divide a Number by 10

Just move the comma one decimal place to the left.
Example 1: 16/10 = 1.6
Example 2: 15.567 / 10 = 1.5567

## TIP 4: Divide a Number by 10no

Just move the comma n decimal places to the left.
Example 1: 16/103 = 0,016
Example 2: 15.567 / 102 = 0,15567

So if we want to do the following division: 12 / 1000. We know that 1000 = 103, then:
12 / 1000 = 12 / 103 = 0,012.

## TIP 5: Multiply a Number by 11

When the number is 2 digits, just add those 2 digits and put the result in the middle. For example, let's do the following multiplication: 26 x 11.

We have the number 26, adding its 2 digits we have 2 + 6 = 8. Ready! Now just put this 8 among them:
the answer is 286. So 26 x 11 = 286.

Another examples:
1) 34x11
we add the digits of the number 34: 3 + 4 = 7
we put the result in their midst: 374. So 34x11 = 374.

2) 81x11
we add the digits of the number 81: 8 + 1 = 9
We put the result in their midst: 891. So 81x11 = 891.

3) 37x11
we add the digits of the number 37: 3 + 7 = 10

As it gave a number greater than 9, then we can't put the whole number in the middle of them. We put only the digit of the units (0) in their midst, and the digit of the ten (1) is added to the first digit of the number: 407. Therefore 37x11 = 407.

When the number is 3 digits, then that number multiplied by 11 will result in a 4 digit number. For example, let's do the following multiplication: 135 x 11.

We have the number 135. Summing the 1st with the 2nd digit of this number we have 1 + 3 = 4. Adding the 2nd to the 3rd digit of this number gives 3 + 5 = 8. These 2 results will be placed in the middle of the number 135, taking your digit from the middle:
1485. Therefore 135 x 11 = 1485.

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