Mental Math Strategies

Why learn mental math?

Mental math means working out answers in your head, without writing every step. It is fast, useful in everyday life, and it builds a deep feel for how numbers work.

The trick is not to "see the whole sum at once." Instead, you use clever strategies to break a hard problem into easy steps. This lesson gives you five strategies you can mix and match.

A strong start is knowing your Number Bonds to 10 and your Times Tables — these facts make every strategy below quicker.

Strategy 1: Add the tens first

Split each number into tens and ones, add the tens, add the ones, then combine.

Work out 34 + 25.

1. Tens: 30 + 20 = 50
2. Ones: 4 + 5 = 9
3. Combine: 50 + 9 = 59

Why it works: tens are easy to add, so doing them first leaves only a small ones sum. You are using place value, just like in Column Addition with Carrying, but in your head.

Strategy 2: Make ten (bridging)

Ten is a friendly number. If you can reach ten on the way, the rest is easy.

Work out 8 + 5.

1. How many more does 8 need to make 10? It needs 2.
2. Take 2 from the 5. That uses up 2 and leaves 3.
3. Now: 8 + 2 = 10, then 10 + 3 = 13.

Why it works: adding to ten and then adding on is far easier than counting up one at a time.

Strategy 3: Round and adjust

When a number is close to a ten (like 19 or 48), round it to the friendly ten, do the easy sum, then adjust.

Work out 47 + 19.

1. Round 19 up to 20.
2. Easy sum: 47 + 20 = 67.
3. You added 1 too many, so subtract it: 67 − 1 = 66.

It works for subtraction too. Work out 63 − 29: round 29 to 30, do 63 − 30 = 33, then add back the 1 you over-removed: 33 + 1 = 34.

Strategy 4: Doubles and near-doubles

If you know your doubles (6 + 6 = 12, 7 + 7 = 14), you can solve nearby sums quickly.

Work out 6 + 7.

1. 7 is one more than 6.
2. Double 6 = 12.
3. Add the extra 1: 12 + 1 = 13.

This is called a near-double. Learning doubles to 10 + 10 unlocks dozens of fast facts.

Strategy 5: Use number bonds

Number bonds are pairs that make a round number. Knowing bonds to 10 and 100 makes subtraction quick.

Work out 100 − 64.

1. Ask: 64 + what = 100?
2. 64 + 6 = 70, then 70 + 30 = 100. That is 6 + 30 = 36.

So 100 − 64 = 36 — found by adding up, not taking away.

Choosing the right strategy

Different sums suit different strategies. Here are some good matches.

Problem	Best strategy	Quick working
34 + 25	Add tens first	50 + 9 = 59
8 + 5	Make ten	8 + 2 + 3 = 13
47 + 19	Round and adjust	67 − 1 = 66
6 + 7	Near-double	12 + 1 = 13
100 − 64	Number bonds	64 + 36 = 100

There is often more than one good way. Pick the one that makes the numbers friendliest for you.

Worked example: combining strategies

Work out 58 + 26 in your head.

1. Round and adjust: treat 58 as 60. 60 + 26 = 86.
2. You added 2 too many, so subtract: 86 − 2 = 84.

Or use add the tens first: 50 + 20 = 70, then 8 + 6 = 14, then 70 + 14 = 84. Both give the same answer — proof your method is sound.

Try it yourself

Solve these in your head, then say which strategy you used.

• 45 + 30 (Answer: 75 — add tens first)
• 9 + 6 (Answer: 15 — make ten)
• 52 + 18 (Answer: 70 — round and adjust)
• 8 + 9 (Answer: 17 — near-double)

Race a partner: who can answer ten quick sums first using these tricks?

Great job!

You now have a toolbox of mental math strategies. The more you practise number bonds and times tables, the faster these tricks become — until you barely have to think.

When numbers get too big for your head, switch to Column Addition with Carrying, or speed up multiplying with The Grid Method for Multiplication.