Addition of numbers close to multiples of ten (e.g. 19, 29, 38, 59 etc.)

**This technique is useful for Mental calculations**

116 + 39 (**Here we can write this 39 as 40-1)**
= 116 + (40 - 1)

= 116 + 40 - 1

= 156 - 1 (**Instead of adding 39 to 116, we just add 40 to 116 (because we can do this without using pen and paper) and later we subtract one from it)**
= 155

Try this.. This is very useful tip while doing calculations.

**Now lets try another example. **
116 + 97

= 116 + (100 - 3)

= 116 + 100 - 3 (**Here, instead of adding 97 to 116, we are just adding a 100 to 116 and then subtracting 3 from it :)**

= 213

Addition of decimals

12.5 + 6.25

= (12 + 0.5) + (6 + 0.25)

= 12 + 6 + 0.5 + 0.25 (**Here we just added the rounded numbers first and later we added the decimal numbers :)**

= 18 + 0.5 + 0.25

= 18.75