To add any two numbers in a faster way, follow the below steps:
Firstly, round up both the numbers by adding or subtracting small numbers.
Add the numbers.
Now subtract or add those values to get the final result.
For example, Add 799 and 299.
Round up 799 to 799+1 = 800 and 299 to 299+1 = 300
800+300 = 1100
Now subtract the added numbers from 1100,
1100-1-1 = 1100-2 = 1099