Step-by-step Maths Level 2: Comparing, ordering and bonds
Part of the Step-by-step Maths Level 2 level 2 check chapter. Chapter overview · whole chapter on one page
Comparing, ordering and bonds
Compare the tens first, then the ones. Use the bonds to 10 and 20 to find missing parts.
Key ideas
- Compare tens first.
- Bonds to 20 add up to 20.
- Bonds to 10 help with bonds to 20.
Method. Compare the tens first. If the tens are the same, compare the ones.
- Compare the tens digits. The tens digit is worth the most.3 and 5
- Tens are different, so the tens decide. 3 tens is fewer than 5 tens.3 tens and 5 tens
- Write the sign. 38 is less than 52.<
Check. 38 < 52 is true.
Watch out. Compare tens first. 61 is greater than 58, because 6 tens is more than 5 tens.
Method. Put the numbers in order, smallest to largest. Find the first one and then the next.
- Look at the tens of each number. The numbers with fewer tens are smaller.45: 4 tens, 27: 2 tens, 63: 6 tens, 38: 3 tens
- Find the first number in the order. It is the smallest, or the largest if we go the other way.27
- Write the numbers in order. Check that each one fits between the ones next to it.27, 38, 45, 63
Check. Read the list again. Each number is bigger than the one before.
Watch out. Compare tens first. 52 comes before 61 because 5 tens is less than 6 tens.
Method. Find the part that makes 20 with the number we know.
- Start with 13. It is the part we know.13
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 13 = 7
- Write the answer. This is the other part of the bond.7
Check. 13 + 7 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Watch out
Watch out. 61 is greater than 58. Compare tens first.
Exam tip
Grown-up tip. Use a number track to check the order. Ask: “What is the bond to 20 with this number?”
Exercise 10B Mixed practice: comparing and bonds
Non-calculatorMethod. Find the part that makes 20 with the number we know.
- Start with 2. It is the part we know.2
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 2 = 18
- Write the answer. This is the other part of the bond.18
Check. 2 + 18 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 10. It is the part we know.10
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 10 = 10
- Write the answer. This is the other part of the bond.10
Check. 10 + 10 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the greatest number by comparing the tens first.
- Look at the tens. The numbers with the most tens are the greatest.2, 3, 7, 1, 8
- Check the ones if two numbers have the same tens. The ones decide between them.26, 33, 75, 14, 83
- Choose the greatest. It is the biggest of the numbers in the list.83
Check. Put the others in order to check: 83 is the greatest of them all.
Watch out. The number with the largest ones digit is not always the greatest.
Method. Find the part that makes 20 with the number we know.
- Start with 16. It is the part we know.16
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 16 = 4
- Write the answer. This is the other part of the bond.4
Check. 16 + 4 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Use a bond to 10 to help. Start from 20 and take away the tens first.
- Take 10 away from 20. That leaves 10.20 - 10 = 10
- Take the rest of 13 away from 10. 13 is 10 and 3, so take away 3 from 10.10 - 3 = 7
- Write the answer. This is the missing part.7
Check. 13 + 7 = 20. Also 10 + 3 + 7 = 20.
Watch out. Use the bond 10 and 10 first. Then the rest is only a small step.
Method. Find the part that makes 20 with the number we know.
- Start with 9. It is the part we know.9
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 9 = 11
- Write the answer. This is the other part of the bond.11
Check. 9 + 11 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the least number by comparing the tens first.
- Look at the tens. The numbers with the most tens are the greatest.4, 3, 2
- Check the ones if two numbers have the same tens. The ones decide between them.49, 33, 21
- Choose the least. It is the smallest of the numbers in the list.21
Check. Put the others in order to check: 21 is the least of them all.
Watch out. The number with the largest ones digit is not always the greatest.
Method. Use a bond to 10 to help. Start from 20 and take away the tens first.
- Take 10 away from 20. That leaves 10.20 - 10 = 10
- Take the rest of 18 away from 10. 18 is 10 and 8, so take away 8 from 10.10 - 8 = 2
- Write the answer. This is the missing part.2
Check. 18 + 2 = 20. Also 10 + 8 + 2 = 20.
Watch out. Use the bond 10 and 10 first. Then the rest is only a small step.
Method. Compare the tens first. If the tens are the same, compare the ones.
- Compare the tens digits. The tens digit is worth the most.2 and 8
- Tens are different, so the tens decide. 2 tens is fewer than 8 tens.2 tens and 8 tens
- Write the sign. 28 is less than 88.<
Check. 28 < 88 is true.
Watch out. Compare tens first. 61 is greater than 58, because 6 tens is more than 5 tens.
Method. Find the greatest number by comparing the tens first.
- Look at the tens. The numbers with the most tens are the greatest.4, 8, 2, 2
- Check the ones if two numbers have the same tens. The ones decide between them.44, 89, 20, 29
- Choose the greatest. It is the biggest of the numbers in the list.89
Check. Put the others in order to check: 89 is the greatest of them all.
Watch out. The number with the largest ones digit is not always the greatest.
Method. Use a bond to 10 to help. Start from 20 and take away the tens first.
- Take 10 away from 20. That leaves 10.20 - 10 = 10
- Take the rest of 17 away from 10. 17 is 10 and 7, so take away 7 from 10.10 - 7 = 3
- Write the answer. This is the missing part.3
Check. 17 + 3 = 20. Also 10 + 7 + 3 = 20.
Watch out. Use the bond 10 and 10 first. Then the rest is only a small step.
Method. Find the least number by comparing the tens first.
- Look at the tens. The numbers with the most tens are the greatest.5, 8, 8, 1
- Check the ones if two numbers have the same tens. The ones decide between them.54, 87, 85, 12
- Choose the least. It is the smallest of the numbers in the list.12
Check. Put the others in order to check: 12 is the least of them all.
Watch out. The number with the largest ones digit is not always the greatest.
Method. Find the part that makes 20 with the number we know.
- Start with 4. It is the part we know.4
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 4 = 16
- Write the answer. This is the other part of the bond.16
Check. 4 + 16 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Use a bond to 10 to help. Start from 20 and take away the tens first.
- Take 10 away from 20. That leaves 10.20 - 10 = 10
- Take the rest of 15 away from 10. 15 is 10 and 5, so take away 5 from 10.10 - 5 = 5
- Write the answer. This is the missing part.5
Check. 15 + 5 = 20. Also 10 + 5 + 5 = 20.
Watch out. Use the bond 10 and 10 first. Then the rest is only a small step.
Method. Compare the tens first. If the tens are the same, compare the ones.
- Compare the tens digits. The tens digit is worth the most.5 and 1
- Tens are different, so the tens decide. 5 tens is more than 1 tens.5 tens and 1 tens
- Write the sign. 58 is greater than 19.>
Check. 58 > 19 is true.
Watch out. Compare tens first. 61 is greater than 58, because 6 tens is more than 5 tens.
Method. Find the part that makes 20 with the number we know.
- Start with 19. It is the part we know.19
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 19 = 1
- Write the answer. This is the other part of the bond.1
Check. 19 + 1 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.