13 — Split the 4 into 1 and 3: 9 + 1 = 10, then 10 + 3 = 13.

Addition and subtraction

Q: There are 7 people on a bus. Then 3 get on and 2 get off. How many are on the bus now?

8 people — 7 + 3 = 10, then 10 − 2 = 8. Work through it one step at a time.

Q: In □ + 4 = 11, what is □?

7 — 11 − 4 = 7. Think of taking 4 off both sides of the balance.

Q: You have ¥100 and buy a snack that costs ¥60. How much change do you get?

¥40 — 100 − 60 = 40, so the change is ¥40.

Q: On the number line, you start at 6 and move 4 steps to the left. Where do you land?

2 — Moving left means subtracting: 6 − 4 = 2.

Where this is used

Pocket money, people on a train, points in a game. The world is full of things going up and going down. Adding and subtracting are the tools we use to say exactly how much they went up or down.

Key points

Adding means moving right

Adding 5 to 3 is the same as starting at 3 on the number line and moving 5 steps to the right. Where you land is the answer: 8.

3 + 5 = 8

Subtracting means moving left

Subtracting moves you back to the left on the number line. Take 3 away from 8 and you step back 3 places, landing on 5.

8 − 3 = 5

Make a 10 and it gets easy

For 9 + 4, split the 4 into 1 and 3. Add the 1 to the 9 to make 10, then add the 3 left over to get 13. Making a 10 first makes the rest much easier.

9 + 4 = 13 (make a 10 first)

Thinking in balance

A pan balance stays level when both sides weigh the same. Looking for the □ in "□ + 3 = 8" is just looking for the weight that keeps it level. The answer is 5. You will use this very same idea later on when you solve equations.

Check yourself 5questions

Tap an option to check

Q1 What is 9 + 4?

Q2 There are 7 people on a bus. Then 3 get on and 2 get off. How many are on the bus now?

Q3 In □ + 4 = 11, what is □?

Q4 You have ¥100 and buy a snack that costs ¥60. How much change do you get?

Q5 On the number line, you start at 6 and move 4 steps to the left. Where do you land?

Jobs that use this

Every job uses this. The ones below are just where it shows up most.

Cashier / shop assistant $34k

Bus or train driver $60k

Cook / chef $40k

Cashier / shop assistant$34k

Get the change wrong and both the shop and the customer lose out. The till does the maths these days, but only someone who can add in their head will notice when the till is wrong.

Maths used: Addition and subtractionMental maths

Bus or train driver$60k

How many people got on, how many got off, how many minutes behind schedule you are. Drivers are adding and subtracting all shift long.

Maths used: Addition and subtractionWorking with times

Cook / chef$40k

Stretching a recipe for 4 to feed 6, or counting how much of an ingredient is left. A kitchen is one calculation after another.

Maths used: Addition and subtractionScaling amounts up and down