## Tuesday

### Build to 10 and 100

The 10s facts are probably the most important ones that you ever learn in mathematics, followed only by the times tables. There are heaps of ways to practice your 10s facts, so that you can build to 10, e.g. 7 + 5 = (well 5 + 5 = 10, so just add 2 = 12). Notice that we used other doubles with that equation as well.

You can also use this for subtraction:
12 - 5 = ?
Well, let's get to 10 first by taking away 2 from 12.
5 is made of 2 and 3, so we'll need to take away another 3 once we reach 10.
12 - 2 (build down to 10) - 3 =
10 - 3 = 7

Here's a game you can play at home, with cards or dice. Pull a card (or roll the dice), and as quickly as you can, pick the number you need to add to reach 10. Do this with 30 cards, then check your answers using a calculator. Then, try to arrange all the cards in pairs (or groups of 3 or 4) that = 10, e.g. 2 + 3 + 5 would be one group, 8 + 2 is another pair.

Check your accuracy with: Alien Abductions.

Then play these very quick and fun game full of awesome practice:
Hit the Button click on Number Bonds in the bottom left corner, try them in this order:
AIM FOR 30 CORRECT ANSWERS WITH 100% ACCURACY on each game!
- Up to 10: Make 10
- Up to 10: Addition within 10
- Up to 20: Make 20

- Up to 20: Addition within 20
- Up to 20: Add 3 digits U + U + U

Extra fun: Submarine Wars

Back to Hit the Button make sure you click on Number Bonds in the bottom left corner and try each of these games, in this order:
AIM FOR 30 CORRECT ANSWERS WITH 100% ACCURACY on each game!
- Make 100 (tens)
- Make 100

Play Making 100.

If you know what adds to 100, you also know what anything subtracted from 100 is, for example:
50 + 50 = 100
100 - 50 = 50

80 + 20 = 100
100 - 20 = 80
AND 100 - 80 = 100

75 + 25 = 100

100 - 25 = 75 (Careful! Not 85, it's 75).
100 - 75 = 25.