You already know your doubles facts, like $6+6=12$ and $8+8=16$. These can help you solve trickier problems in a flash. This strategy is called 'near doubles'.

Let's try adding $6+7$. Notice that 7 is just one more than 6. So, you can think of this problem as a doubles fact with an extra one.

First, do the double: $6+6=12$. Then, just add the extra one: $12+1=13$. So, $6+7=13$. Easy!

This works the other way, too. What about $8+9$? You can think of it as double 8 plus 1, or double 9 minus 1.

Using double 8: $8+8=16$ $16+1=17$

Using double 9: $9+9=18$ $18-1=17$

Both ways give you the same answer. You can pick whichever double you find easier to remember.

The number ten is a friendly number in maths. It's often easier to add numbers to ten than to any other number. The 'bridge to ten' strategy uses this to our advantage.

Let's figure out $8+5$. Our goal is to make the first number, 8, into a ten. How many more does 8 need to become 10? It needs 2.

We can take that 2 from the 5. If we split 5 into 2 and 3, we can give the 2 to the 8. This makes our new problem much simpler.

Let's try another one: $9+7$. Nine needs one more to make ten. We take 1 from the 7, leaving 6. So, $9+7$ becomes $10+6$, which is 16. With a little practice, you can do this in your head.

Addition and subtraction are closely related. They are inverse operations, which means they undo each other. Thinking about them this way can help you solve problems.

If you know that $7+8=15$, you also know two subtraction facts:

• $15-7=8$
• $15-8=7$

These three numbers, 7, 8, and 15, make up a fact family. Understanding this relationship helps you check your work and solve for missing numbers.

A great way to see this relationship is with a part-part-whole model. In an addition problem, the two numbers you add are the 'parts'. The answer you get is the 'whole'. For $7+8=15$, the parts are 7 and 8, and the whole is 15.

This model shows that if you have the whole and one part, you can find the other part by subtracting. If you have the two parts, you can find the whole by adding. This is a powerful tool for solving problems where a number is missing.

Using these strategies helps you calculate faster and with more confidence. Keep practising them until they become second nature.