Subtraction fact · doubles
20 − 10 = 10
Twenty minus ten is ten. 20 is double 10, so taking away 10 leaves the other half.
See 20 − 10
20 counters, 10 crossed out, 10 left.
It's half of a double
- Remember the double: 10 + 10 = 20.
- Take one of those 10s away.
- The other 10 is left, so 20 − 10 = 10.
Its fact family has two facts
10, 10 and 20 go together, so learning one of these helps with all of them. See the family.
Practice 20 − 10 in a game
A fact sticks when a child has to pull it from memory again and again. In this game 20 − 10 keeps coming back between the other facts in its family.
Every round leans on 20 − 10
Free to play · no signup · works on phones, tablets and computers
Quick quiz
20 − 10 FAQ
What is 20 − 10?
20 − 10 = 10. In words: twenty minus ten is ten.
How can I check 20 − 10 = 10?
Add back: 10 + 10 = 20. If the addition gives the number you started with, the subtraction is right.
What grade learns 20 − 10?
This is a first and second grade fact. Common Core has children subtract within 20 in first grade (1.OA.C.6) and do it fluently with mental strategies in second grade (2.OA.B.2).
Is Sumtown really free?
Yes. The whole game plays free in your browser, with no signup, no ads and no time limit. All fourteen mini games are in it. An iPhone app is on its way, and you can read what it will add.
An app is on its way
We're building a Sumtown app for iPhone with the parts that need a real app: offline play for car rides, a town map that remembers how far your child got, and a parent report on every fact. Until then, the whole game is free right here.
Coming soon on theApp Store