Solution:
Consider the sum of following numbers
1. 23 +7=20 +10
2. 17 + 127=20+130
3. 5478 + 126= 5480 + 130
4. 65899+58423=65900+ 58420
Converted all these numbers to nearest tens,and then we can add these numbers Quickly.
As to add these numbers , we convert addends to nearest tens while solving an addition problem , it helps us in adding the numbers easily . The number when rounded having unit digit zero, makes our calculations easy.