Year 2: Adding and subtracting two two-digit numbers
Part of the Year 2 adding and subtracting chapter. Chapter overview · whole chapter on one page
Adding and subtracting two two-digit numbers
To add two two-digit numbers, split each number into tens and ones.
Add the tens. Then add the ones. Then put the two answers together.
For 36 + 27: 30 + 20 = 50. 6 + 7 = 13. 50 + 13 = 63.
A column layout keeps the tens above the tens. The ones go above the ones.
Key ideas
- Tens go with tens. Ones go with ones.
- Split each number into tens and ones.
- If the ones make 10 or more, make a new ten.
- Check a sum by taking one number away from the total.
| 3 | 6 | |
| + | 2 | 7 |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the ones. 6 + 7 = 13. That is 10 or more, so make a new ten.6 + 7 = 13
- Write the ones and carry the ten. 13 ones is 1 ten and 3 ones. Write 3; carry 1 ten.13 = 1 ten and 3 ones
- Add the tens, with the new ten. 3 tens + 2 tens + 1 ten = 6 tens.30 + 20 + 10 = 60
- Put the parts together. 60 and 3 make 63.60 + 3 = 63
Check. Take 27 away from 63. You get 36. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 5 | 8 | |
| − | 2 | 3 |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Take away the tens. 5 tens − 2 tens = 3 tens.50 − 20 = 30
- Take away the ones. 8 ones − 3 ones = 5 ones.8 − 3 = 5
- Put the parts together. 30 and 5 make 35.30 + 5 = 35
Check. Add 23 to 35. You get 58. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 1 | ||
| 4 | 5 | |
| + | 3 | 8 |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the ones. 5 + 8 = 13. That is 10 or more, so make a new ten.5 + 8 = 13
- Write the ones and carry the ten. 13 ones is 1 ten and 3 ones. Write 3; carry 1 ten.13 = 1 ten and 3 ones
- Add the tens, with the new ten. 4 tens + 3 tens + 1 ten = 8 tens.40 + 30 + 10 = 80
- Put the parts together. 80 and 3 make 83.80 + 3 = 83
Check. Take 38 away from 83. You get 45. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
Watch out
Watch out: when the ones make 10 or more, carry a new ten to the tens. 6 + 7 = 13 makes 1 new ten.
Exam tip
Grown-up tip. Write the sum on squared paper, one digit in each box. Ask: “How many ones? Do we need a new ten?”
Exercise 2D Adding and subtracting two two-digit numbers
Non-calculator| 3 | 4 | |
| + | 2 | 5 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the tens. 3 tens + 2 tens = 5 tens.30 + 20 = 50
- Add the ones. 4 ones + 5 ones = 9 ones.4 + 5 = 9
- Put the parts together. 50 and 9 make 59.50 + 9 = 59
Check. Take 25 away from 59. You get 34. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 5 | 2 | |
| + | 3 | 1 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the tens. 5 tens + 3 tens = 8 tens.50 + 30 = 80
- Add the ones. 2 ones + 1 ones = 3 ones.2 + 1 = 3
- Put the parts together. 80 and 3 make 83.80 + 3 = 83
Check. Take 31 away from 83. You get 52. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 4 | 6 | |
| + | 1 | 7 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the ones. 6 + 7 = 13. That is 10 or more, so make a new ten.6 + 7 = 13
- Write the ones and carry the ten. 13 ones is 1 ten and 3 ones. Write 3; carry 1 ten.13 = 1 ten and 3 ones
- Add the tens, with the new ten. 4 tens + 1 ten + 1 ten = 6 tens.40 + 10 + 10 = 60
- Put the parts together. 60 and 3 make 63.60 + 3 = 63
Check. Take 17 away from 63. You get 46. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 6 | 8 | |
| − | 3 | 5 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Take away the tens. 6 tens − 3 tens = 3 tens.60 − 30 = 30
- Take away the ones. 8 ones − 5 ones = 3 ones.8 − 5 = 3
- Put the parts together. 30 and 3 make 33.30 + 3 = 33
Check. Add 35 to 33. You get 68. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 8 | 5 | |
| − | 2 | 7 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- The ones are not enough, so exchange a ten. 5 ones is less than 7 ones, so take 1 ten.8 tens and 5 ones = 7 tens and 15 ones
- Take away the ones. 15 ones − 7 ones = 8 ones.15 − 7 = 8
- Take away the tens. 7 tens − 2 tens = 5 tens.70 − 20 = 50
- Put the parts together. 50 and 8 make 58.50 + 8 = 58
Check. Add 27 to 58. You get 85. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 5 | 7 | |
| + | 3 | 6 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the ones. 7 + 6 = 13. That is 10 or more, so make a new ten.7 + 6 = 13
- Write the ones and carry the ten. 13 ones is 1 ten and 3 ones. Write 3; carry 1 ten.13 = 1 ten and 3 ones
- Add the tens, with the new ten. 5 tens + 3 tens + 1 ten = 9 tens.50 + 30 + 10 = 90
- Put the parts together. 90 and 3 make 93.90 + 3 = 93
Check. Take 36 away from 93. You get 57. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
| 6 | 4 | |
| + | 2 | 8 |
| ? | ? | |
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the ones. 4 + 8 = 12. That is 10 or more, so make a new ten.4 + 8 = 12
- Write the ones and carry the ten. 12 ones is 1 ten and 2 ones. Write 2; carry 1 ten.12 = 1 ten and 2 ones
- Add the tens, with the new ten. 6 tens + 2 tens + 1 ten = 9 tens.60 + 20 + 10 = 90
- Put the parts together. 90 and 2 make 92.90 + 2 = 92
Check. Take 28 away from 92. You get 64. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the tens. 2 tens + 4 tens = 6 tens.20 + 40 = 60
- Add the ones. 3 ones + 6 ones = 9 ones.3 + 6 = 9
- Put the parts together. 60 and 9 make 69.60 + 9 = 69
Check. Take 46 away from 69. You get 23. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Take away the tens. 7 tens − 3 tens = 4 tens.70 − 30 = 40
- Take away the ones. 5 ones − 2 ones = 3 ones.5 − 2 = 3
- Put the parts together. 40 and 3 make 43.40 + 3 = 43
Check. Add 32 to 43. You get 75. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
Key words. A written method splits the numbers into tens and ones.
Method. Split each number into tens and ones. Work with the tens, then the ones.
- Add the ones. 8 + 4 = 12. That is 10 or more, so make a new ten.8 + 4 = 12
- Write the ones and carry the ten. 12 ones is 1 ten and 2 ones. Write 2; carry 1 ten.12 = 1 ten and 2 ones
- Add the tens, with the new ten. 3 tens + 4 tens + 1 ten = 8 tens.30 + 40 + 10 = 80
- Put the parts together. 80 and 2 make 82.80 + 2 = 82
Check. Take 44 away from 82. You get 38. ✓
Watch out. Tens go with tens, and ones go with ones. Do not mix them up.
Method. Altogether means add. Add the two amounts.
- Find the first amount. There are 36 apples to start.36 apples
- Add the second amount. There are 27 more apples.36 + 27 = 63
- Write the answer. Altogether means add.63
Check. Take 27 away from 63. You get 36. ✓
Watch out. Read the question again. Did we add or did we take away?
Method. Giving away means take away. Subtract the amount that goes.
- Find the amount to start. There are 84 marbles to start.84 marbles
- Take away the amount that goes. 39 marbles go away.84 − 39 = 45
- Write the answer. What is left is the answer.45
Check. Add 39 back to 45. You get 84. ✓
Watch out. Start with the bigger amount. Take away the smaller amount.
| 4 | 7 | |
| + | 2 | 8 |
Method. Work out the sum or difference, then compare it with what was said.
- Work out 47 + 28. Use a method that you know.47 + 28 = 75
- Compare with the claim. The claim says 65, but the answer is 75.No. 47 + 28 = 75
Check. Take 28 away from 75. You get 47. ✓
Watch out. Check the tens first, then the ones. A carry or an exchange is easy to forget.