Adding and taking away with tens and ones
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What you will learn
By the end, you can add or take away two-digit numbers in your head by using the tens first, then the ones.
At the school fair, Ben scores 34 with his first bean bag and 25 with his second. He does not count on his fingers. He jumps 20, then 5, and shouts the total before anyone else: 59!
Read the explanation
Two-digit numbers are made of tens and ones. To add, add the tens first, then the ones. To take away, take away the tens first, then the ones. If the ones do not fit, swap ten ones for one ten, or one ten for ten ones.
- Tens first: they are the big jumps.
- Ones last: they are the small steps.
- Check with the opposite: 59 − 25 should take you back to 34.