61
57
73
65
Add all at once.
Align the numbers by their digits, add from right to left, carrying over if needed.
Subtract then add.
Add from left to right.
74
72
76
78
Round it down to nearest ten.
You carry over the extra value to the next column.
Start over the addition.
Ignore the remaining value.
68
72
70
74
100
90
110
105
83
80
79
82
To make it faster.
To ensure that each digit is in the right column for accurate addition.
To avoid subtraction.
To skip carrying over.
41
40
42
39
You can reverse the addition to subtraction or use estimation.
Add it again quickly.
Use a calculator.
Estimate using multiplication.
90
100
95
98
84
86
85
83
Write the ones digit in that column and carry the tens digit to the next column.
Write the total in the next column.
Carry over the total without writing.
Only write the tens digit.
94
96
95
92
Paper and pencil help keep track of carrying over and organizing numbers.
To use multiple colors.
To add without understanding.
For faster calculation.