Step-by-step Maths Level 2: Adding a multiple of 10
Part of the Step-by-step Maths Level 2 adding and subtracting within 100 chapter. Chapter overview · whole chapter on one page
Adding a multiple of 10
Adding 10, 20, 30 and so on changes only the tens. The ones stay the same.
Add the tens first, then keep the ones.
Key ideas
- Adding 10 adds one ten.
- Adding 20 adds two tens.
- The ones digit does not change.
Method. Add the tens together. The ones stay the same.
- Find the tens of 20. 20 is 2 tens.20 = 2 tens
- Add the tens. 3 tens + 2 tens = 5 tens.3 + 2 = 5
- Keep the ones. The ones are still 4.5 tens and 4 ones
- Write the answer. 54
Check. 34 + 20 goes up by 2 tens. The answer is 54.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 30. 30 is 3 tens.30 = 3 tens
- Add the tens. 4 tens + 3 tens = 7 tens.4 + 3 = 7
- Keep the ones. The ones are still 2.7 tens and 2 ones
- Write the answer. 72
Check. 42 + 30 goes up by 3 tens. The answer is 72.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 40. 40 is 4 tens.40 = 4 tens
- Add the tens. 1 tens + 4 tens = 5 tens.1 + 4 = 5
- Keep the ones. The ones are still 5.5 tens and 5 ones
- Write the answer. 55
Check. 15 + 40 goes up by 4 tens. The answer is 55.
Watch out. Adding a multiple of 10 changes only the tens digit.
Watch out
Watch out. 34 + 20 is 54, not 74. Only the tens go up by 2.
Exam tip
Grown-up tip. Count in tens from the number. Ask: “How many tens have we added?”
Exercise 7B Practice: adding multiples of 10
Non-calculatorMethod. Add the tens together. The ones stay the same.
- Find the tens of 50. 50 is 5 tens.50 = 5 tens
- Add the tens. 1 tens + 5 tens = 6 tens.1 + 5 = 6
- Keep the ones. The ones are still 9.6 tens and 9 ones
- Write the answer. 69
Check. 19 + 50 goes up by 5 tens. The answer is 69.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 10. 10 is 1 tens.10 = 1 tens
- Add the tens. 8 tens + 1 tens = 9 tens.8 + 1 = 9
- Keep the ones. The ones are still 4.9 tens and 4 ones
- Write the answer. 94
Check. 84 + 10 goes up by 1 tens. The answer is 94.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 20. 20 is 2 tens.20 = 2 tens
- Add the tens. 4 tens + 2 tens = 6 tens.4 + 2 = 6
- Keep the ones. The ones are still 1.6 tens and 1 ones
- Write the answer. 61
Check. 41 + 20 goes up by 2 tens. The answer is 61.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 20. 20 is 2 tens.20 = 2 tens
- Add the tens. 4 tens + 2 tens = 6 tens.4 + 2 = 6
- Keep the ones. The ones are still 8.6 tens and 8 ones
- Write the answer. 68
Check. 48 + 20 goes up by 2 tens. The answer is 68.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 20. 20 is 2 tens.20 = 2 tens
- Add the tens. 2 tens + 2 tens = 4 tens.2 + 2 = 4
- Keep the ones. The ones are still 6.4 tens and 6 ones
- Write the answer. 46
Check. 26 + 20 goes up by 2 tens. The answer is 46.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 10. 10 is 1 tens.10 = 1 tens
- Add the tens. 5 tens + 1 tens = 6 tens.5 + 1 = 6
- Keep the ones. The ones are still 5.6 tens and 5 ones
- Write the answer. 65
Check. 55 + 10 goes up by 1 tens. The answer is 65.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 60. 60 is 6 tens.60 = 6 tens
- Add the tens. 2 tens + 6 tens = 8 tens.2 + 6 = 8
- Keep the ones. The ones are still 5.8 tens and 5 ones
- Write the answer. 85
Check. 25 + 60 goes up by 6 tens. The answer is 85.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 60. 60 is 6 tens.60 = 6 tens
- Add the tens. 3 tens + 6 tens = 9 tens.3 + 6 = 9
- Keep the ones. The ones are still 2.9 tens and 2 ones
- Write the answer. 92
Check. 32 + 60 goes up by 6 tens. The answer is 92.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 40. 40 is 4 tens.40 = 4 tens
- Add the tens. 4 tens + 4 tens = 8 tens.4 + 4 = 8
- Keep the ones. The ones are still 4.8 tens and 4 ones
- Write the answer. 84
Check. 44 + 40 goes up by 4 tens. The answer is 84.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 50. 50 is 5 tens.50 = 5 tens
- Add the tens. 3 tens + 5 tens = 8 tens.3 + 5 = 8
- Keep the ones. The ones are still 7.8 tens and 7 ones
- Write the answer. 87
Check. 37 + 50 goes up by 5 tens. The answer is 87.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 10. 10 is 1 tens.10 = 1 tens
- Add the tens. 8 tens + 1 tens = 9 tens.8 + 1 = 9
- Keep the ones. The ones are still 3.9 tens and 3 ones
- Write the answer. 93
Check. 83 + 10 goes up by 1 tens. The answer is 93.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 20. 20 is 2 tens.20 = 2 tens
- Add the tens. 7 tens + 2 tens = 9 tens.7 + 2 = 9
- Keep the ones. The ones are still 4.9 tens and 4 ones
- Write the answer. 94
Check. 74 + 20 goes up by 2 tens. The answer is 94.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 10. 10 is 1 tens.10 = 1 tens
- Add the tens. 8 tens + 1 tens = 9 tens.8 + 1 = 9
- Keep the ones. The ones are still 1.9 tens and 1 ones
- Write the answer. 91
Check. 81 + 10 goes up by 1 tens. The answer is 91.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 20. 20 is 2 tens.20 = 2 tens
- Add the tens. 5 tens + 2 tens = 7 tens.5 + 2 = 7
- Keep the ones. The ones are still 3.7 tens and 3 ones
- Write the answer. 73
Check. 53 + 20 goes up by 2 tens. The answer is 73.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 10. 10 is 1 tens.10 = 1 tens
- Add the tens. 4 tens + 1 tens = 5 tens.4 + 1 = 5
- Keep the ones. The ones are still 6.5 tens and 6 ones
- Write the answer. 56
Check. 46 + 10 goes up by 1 tens. The answer is 56.
Watch out. Adding a multiple of 10 changes only the tens digit.
Method. Add the tens together. The ones stay the same.
- Find the tens of 10. 10 is 1 tens.10 = 1 tens
- Add the tens. 8 tens + 1 tens = 9 tens.8 + 1 = 9
- Keep the ones. The ones are still 5.9 tens and 5 ones
- Write the answer. 95
Check. 85 + 10 goes up by 1 tens. The answer is 95.
Watch out. Adding a multiple of 10 changes only the tens digit.