Mental strategies: split and compensate
Name: _____________________ Date: __________
Show your thinking with numbers, words, or a drawing.
1. Split into tens and ones: 57 + 24 = 50 + 20 + 7 + 4 = ?
2. Split into tens and ones: 34 + 18 = 30 + 10 + 4 + 8 = ?
3. Split into tens and ones: 76 + 16 = 70 + 10 + 6 + 6 = ?
4. Split into tens and ones: 42 + 49 = 40 + 40 + 2 + 9 = ?
5. Split into tens and ones: 17 + 34 = 10 + 30 + 7 + 4 = ?
Answer key ยท Mental strategies: split and compensate
1. 81
Tens: 50 + 20 = 70. Ones: 7 + 4 = 11.
11 is 1 ten and 1 ones, so 70 + 11 = 81.
So 57 + 24 = 81.
2. 52
Tens: 30 + 10 = 40. Ones: 4 + 8 = 12.
12 is 1 ten and 2 ones, so 40 + 12 = 52.
So 34 + 18 = 52.
3. 92
Tens: 70 + 10 = 80. Ones: 6 + 6 = 12.
12 is 1 ten and 2 ones, so 80 + 12 = 92.
So 76 + 16 = 92.
4. 91
Tens: 40 + 40 = 80. Ones: 2 + 9 = 11.
11 is 1 ten and 1 ones, so 80 + 11 = 91.
So 42 + 49 = 91.
5. 51
Tens: 10 + 30 = 40. Ones: 7 + 4 = 11.
11 is 1 ten and 1 ones, so 40 + 11 = 51.
So 17 + 34 = 51.
Try it together
Choose a question from the printable. Use objects or a drawing to show your thinking, then explain your method to someone at home.