Today is rung 9 of 10 on this topic
Mental strategies within 100
Can do: Adds and subtracts two-digit numbers in their head using tens, doubles and near-doubles.
Why it matters
Written methods are for hard numbers. A child who writes out 30 + 25 in columns has lost the number sense that makes maths quick and checkable.
What it looks like when it's wobbly
Reaches for pencil and paper for everything, including 40 + 30.
⏱️ Two-minute check
In your head: 40 + 30, 25 + 25, 56 + 20, 71 − 40.
Solid looks like: Three of four, no writing, within a few seconds each.
The full activity for this topic · 5 minutes
Head Maths in the Car
- 1Do tens first: 30 + 40, 60 − 20. These should be instant.
- 2Then add tens to any number: 26 + 30. Point out only the tens digit changes.
- 3Then doubles: 25 + 25, 30 + 30, and near-doubles: 25 + 26.
- 4Ask them to say the strategy, not just the answer.
- 5Keep it to five questions and stop while it's still easy.
If it's too hard
Multiples of ten only.
If it's too easy
Bridging: 48 + 7 by getting to 50 first, then adding the rest.
Say this
"Don't write it. What's the quickest way in your head? Tell me how you got there."