You add every day, even before you know the word. Two sweets in one hand and three in the other: how many sweets altogether? Four children at the table and one more comes to sit: how many children now? Each time you put two groups together and count the whole lot.
This lesson is the first step in all the adding you will ever do. The numbers are small, so you can use your fingers, beads or a number line to check every answer. Take it slowly and say each sum out loud. Every answer here stays at ten or below.
The number ladder
Before adding anything, say the numbers in order. Going up is called ascending order:
Going down is called descending order:
Think of it as a ladder of numbers. Adding is climbing up. Taking away is climbing down. To work out , stand on 4 and take three steps up: 5, 6, 7. So .
Count the hops, not the marks. You start on 4, so the first hop takes you to 5.
Adding zero
Zero means nothing at all. If you have four sweets and somebody gives you nothing, you still have four sweets.
| Sum | Sum |
|---|---|
Remember. When you add zero to a number, the answer is that same number. On the ladder you take no steps at all.
Adding one
Adding one is one step up the ladder. The answer is the next number you say when you count.
| Sum | Sum |
|---|---|
A basket has 8 apples. Amma puts in 1 more. Count on from 8 by one: 9. So apples.
Adding two and three
Adding two is two steps up. Adding three is three steps up.
| Adding two | Adding three |
|---|---|
Example 1
Work out .
Stand on 5. Take three steps up and say only the new numbers: 6, 7, 8. You land on 8.
Example 2
Work out .
Stand on 7. Two steps up: 8, 9.
Start from the bigger number
Look at . You could stand on 2 and take seven steps. That is a long walk, and it is easy to lose count.
Turn it round instead. Stand on 7 and take two steps: 8, 9. You land on 9.
Turning a sum round never changes the answer. Two sweets and seven sweets make the same pile as seven sweets and two sweets. So always start from the bigger number and count on the smaller one.
Example 3
Work out .
Start on the bigger number, 8. One step up: 9. So .
Example 4
Work out .
Start on 5. Two steps up: 6, 7. So .
Doubles
A double is a number added to itself. Doubles are worth learning by heart.
| Double | Double |
|---|---|
You can see doubles on your own body. Two hands, each with 5 fingers, make .
Doubles help with the sums next door to them. A sum that is one more than a double is called a near double. If you know , then is just one more:
The pairs that make ten
These five pairs are called the tens complements, or the tens partners. Each number has one partner that takes it all the way to ten.
| Number | Its partner | Why |
|---|---|---|
In each row of the picture the two colours fill all ten places. Hold up ten fingers and fold down 6. The 4 fingers still standing are the partner of 6.
Remember. Learn the five pairs: 9 and 1, 8 and 2, 7 and 3, 6 and 4, 5 and 5. You will use them in nearly every lesson that follows.
Common mistakes
- Counting the starting number as a step. For some children say "4, 5, 6" and answer 6. Start on 4 and say only the new numbers: 5, 6, 7.
- Thinking adding zero makes zero. is 7, not 0. Nothing was added, so nothing changed.
- Counting on from the smaller number. It is slow and easy to get wrong. For , start on 6.
- Mixing up the partners of ten. 6 goes with 4, not with 3. Check on ten fingers.
Key terms
- Add: put two groups together and find how many there are altogether. The sign is .
- Ascending order: numbers going up, such as 0, 1, 2, 3.
- Descending order: numbers going down, such as 10, 9, 8, 7.
- Count on: start on one number and say the next numbers, one for each thing you add.
- Double: a number added to itself, such as .
- Tens complements: the pairs that add up to ten.
Practice
- What is the partner of 8 that makes ten?
Answers
Show answers
- . Adding zero changes nothing.
- . Start on 7 and count on 2.
- . Start on 8 and count on 1.
- , one more than the double .
- The partner of 8 is 2, because .