Number Addition Result Checking Tricks

Number Addition Result Checking Tricks
1. Add any number
2. Remove combination of 9 from numbers and add remaining number (it is must come below 9)
3. Make a single digit from the result value (it is also must be below 9)

Both 2 and 3 result is same means, your calculation is correct.

Example
674 + 7321 + 87 + 4 = 8086

6, 7, 4, 7, 3, 2, 1, 8, 7, 4
here,
7 + 2 (=9), 7 + 7 + 4 (=18 =2*9), 6 + 3 (=9), 1 + 8 (=9), 4

8 + 0 + 8 + 6 = 22
2 + 2 = 4

We got both result is 4, so our calculation is correct.