as y2 add sub 100

What you'll learn

1. 1

   Adding and subtracting within 100 works best if you deal with the tens and the ones separately.

2. 2

   36 + 27. Tens: 30 + 20 = 50. Ones: 6 + 7 = 13. That is 50 + 13 = 63.

3. 3

   What is 45 + 23?

4. 4

   Adding can be done in any order, but subtracting cannot. 5 + 3 is the same as 3 + 5, but 8 − 3 is not the same as 3 − 8.

5. 5

   7 + 48. Swap it round to 48 + 7 and count on: 48, 49, 50... 55. Much easier than counting on 48 times.

6. 6

   What is 84 − 31?

7. 7

   Which of these can you safely swap round?