How to play Make 20
- A number block from 1 to 19 waits above the board. Tap a column to drop it there.
- If it lands next to a block that makes 20 with it, both blocks disappear: 1 and 19, 6 and 14, 10 and 10, and so on.
- Blocks above a gap fall down and can make 20 with the blocks they land next to.
- The game ends when a column is full to the top.
Stuck? Press Hint to see a column where your block makes a bond. Every bond you make, the adder above the board eats it and grows one block longer.
Easy gives more blocks that fit somewhere, Tricky fewer.
For parents and teachers
Make 20 practises number bonds to 20, built on the bonds to 10: 7 and 3 make 10, so 17 and 3 make 20, and so do 13 and 7. Recalling addition facts to 20 is a Year 2 objective in England’s national curriculum; the US Common Core asks for adding and subtracting within 20 in grade 1 (1.OA.C.6).
A guide: ages 6 to 8, once the bonds to 10 are secure.
The Block Adder games
- Make 5: Find two blocks that add up to 5, like 2 and 3.
- Make 10: Find two blocks that add up to 10, like 3 and 7.
- Make 20: Find two blocks that add up to 20, like 12 and 8.
- Make 100: Find two tens that add up to 100, like 30 and 70.
- Sums to 10: Drop each sum on its answer: 4 + 3 goes on a 7.
- Sums to 20: Drop each sum on its answer: 12 − 3 goes on a 9.
Questions
How do bonds to 20 relate to bonds to 10?
Every bond to 20 with a teen number is a bond to 10 with a ten added: 4 + 6 = 10, so 14 + 6 = 20. Encourage your child to look for that.
Why are there no dots in Make 20?
The numbers go past 10, so a ten-frame no longer fits on a block. Make 10 and Make 5 have dots.
Is it safe for children?
Block Adder has no ads, no chat, no sign-up and no tracking. Nothing your child does is sent anywhere: the game in progress, the best scores and the statistics are kept only in this browser.
Does it work on a phone or tablet?
Yes. Tap a column to drop the block there. It fits a phone held upright, and it works with a mouse or the keyboard on a computer.
Keyboard
| 1 to 5 | Drop into that column |
|---|---|
| Left and right arrows | Move between columns |
| Enter or Space | Drop into the chosen column |
| H | Hint |