What Is a Number Bond?
A number bond shows how a number splits into two parts. The whole sits in the top circle and the two parts sit in the circles underneath, joined to it by lines. When 10 is at the top and 3 and 7 are below, the diagram says that 3 and 7 together make 10. It also says, without any extra work, that 10 take away 3 is 7 and 10 take away 7 is 3. That is why Singapore schools introduce the diagram in K2 and keep using it all through lower primary: one picture holds an addition fact and both of its subtraction facts.
Children first meet number bonds with real objects: a handful of buttons pushed into two piles, or a row of counters split by a pencil. The bond explorer on this page does the same thing on screen. Once your child can split a small number in several ways without counting from one, the bonds start to stick as facts, and the number bond questions in the practice round check how quickly they come back.
Place Value: Tens and Ones
Place value is the idea that the position of a digit tells you what it is worth. In 47, the 4 is not four, it is four tens, or forty. Base-ten blocks make that visible: a single cube is one, a rod of ten cubes is ten, and in Primary 2 a flat square of ten rods is a hundred. When a child builds 47 out of four rods and seven cubes, the written number stops being two digits side by side and becomes an amount they can see.
The most useful habit to build is exchanging. Ten ones make one ten, and ten tens make one hundred. A child who has seen 3 tens and 17 ones turned into 4 tens and 7 ones will understand regrouping in column addition and subtraction long before the written method is taught. That is why the build activity never marks 3 tens and 17 ones as wrong for 47. It is right, but the page asks for the swap so that every place holds 0 to 9.
How to Use This Page
- Pick the school year and an activity, then the number of questions, and press Start. Ten questions take most children about five minutes.
- Number bonds: type the missing number in the empty circle. In K2 the counters below the diagram can be counted, and in P1 there is a button to show them when your child is stuck.
- Build the number: press + and − under each column to add or remove hundreds, tens and ones until the blocks show the number asked for, then press Check.
- Read the blocks: count the blocks and type the number they make. Some questions have more than nine ones or tens on purpose, to practise exchanging.
- Tens and ones: fill in the boxes, such as 47 = □ tens □ ones, or 300 + □ + 7 = 347.
- Fix the ones you missed. At the end, only the questions that went wrong come back, with the picture from the first try fresh in mind.
Activities by Level
| Level | Number bonds | Place value |
|---|---|---|
| K2 | Bonds of numbers 3 to 10, with counters in a ten frame to count | Numbers 11 to 20 as 1 ten and some ones |
| P1 | Bonds within 10, teen numbers as 10 and some ones, and pairs of single digits that make 11 to 18 | Numbers to 100: tens and ones, 40 + 7, the value of a digit, exchanging 10 ones for a ten |
| P2 | Bonds of tens (30 and 50 make 80), bonds of 100, and two-digit bonds | Numbers to 1000: hundreds, tens and ones, expanded form, the value of a digit, exchanging |
The levels follow the usual order in Singapore preschools and primary schools, where children count to 20 in K2, work with numbers to 100 in Primary 1 and to 1000 in Primary 2. Schools differ a little in pace, so move up or down freely.
Tips for Parents and Teachers
- Say the bond both ways. After 3 and 7 make 10, ask “so what is 10 take away 7?” The answer is already on the diagram.
- Make ten first. To add 8 + 5, split the 5 into 2 and 3, make 10 with the 2, and add the 3 to get 13. Bonds of 10 are what make this work.
- Use real objects too. Ice-cream sticks bundled in tens with a rubber band are a cheap set of tens rods. Bundling and unbundling them is exchanging.
- Read numbers in tens. When you see a price tag or a bus number, ask how many tens it has. Little questions often beat long sessions.
- Keep it short. Five or ten questions a day builds quicker recall than an hour once a week. Our math flash cards train the addition facts at speed, and the worksheet generator prints number bond and place value sheets with answer keys.
Nothing to Install, Nothing Stored on Our Server
The practice runs entirely in your browser on any phone, tablet or computer. There is no account and no download. The last level and activity you chose are remembered on this device, and nothing about your child’s answers is sent to us.
Frequently Asked Questions
A number bond shows how a number splits into two parts. The whole sits in the top circle and the two parts sit in the circles below, joined by lines: 10 at the top with 3 and 7 below means 3 and 7 make 10. Singapore schools use the diagram from K2 so that children see addition and subtraction as two sides of the same fact.
The bonds of 10 (1 and 9, 2 and 8, 3 and 7, 4 and 6, 5 and 5) matter most, because adding and subtracting across ten in Primary 1 uses them all the time. After that come the bonds of every number up to 10, then numbers to 20 split into 10 and some ones, and in Primary 2 the bonds of 100 in tens.
K2 has number bonds within 10 with counters to count, and numbers 11 to 20 as one ten and some ones. P1 has bonds within 20 and numbers to 100 in tens and ones. P2 has bonds of tens and bonds to 100, and numbers to 1000 in hundreds, tens and ones. If your child hesitates on most questions, drop a level for a few rounds.
3 tens and 17 ones really do make 47, so it is not marked wrong. But in the place value chart each place holds only 0 to 9, so the page asks your child to swap 10 ones for 1 ten. That swap is the same idea as regrouping in Primary 2 addition and subtraction.
Yes. There is no account, no download and no limit on rounds. It works in any browser on a phone, tablet or computer, and nothing about your child’s answers is sent to us.