Addition and subtraction games

What these addition and subtraction games practice

By the end of 1st grade, the Common Core standards expect children to add and subtract fluently within 10 (1.OA.C.6). By the end of 2nd grade, they should "know from memory all sums of two one-digit numbers" (2.OA.B.2), which takes in every addition fact up to 9 + 9 and the subtraction facts that undo them. These games cover all of those facts, plus the 10s, in three ways:

You choose Addition, Subtraction or Both, and Within 10 (sums up to 10) or Within 20 (any two numbers from 0 to 10). Answers can be typed or picked from four choices.

How the game adapts to your child

Every fact has its own record, kept in your browser. The game uses five boxes:

• A fact answered right within three seconds moves up a box.
• A fact answered right but slowly stays where it is. Your child knows it, but is still counting.
• A missed fact goes back to the first box and comes back in the same session.
• Facts in higher boxes wait longer before they come back: a day, three days, a week, three weeks.

Practice picks due facts first, adds a few new ones at a time, and fills the rest with facts that are nearly due. This is spaced practice, one of the most reliable findings in learning research: Cepeda and colleagues' 2006 review found that spreading practice out beats massing it together across hundreds of studies.

The addition strategies children use

Children don't memorize 121 facts one at a time. They learn a handful of patterns that cover most of them, then practice until the patterns become instant. When your child misses a fact, the game shows the strategy that fits it, and the Learn tab shows each fact as dots in rows of ten.

Standard 1.OA.C.6 names several of these directly: counting on, making ten, decomposing a number to get to ten, and using the relationship between addition and subtraction. Andrew Baroody's 2006 article on basic facts explains why: children who reason from facts they know to facts they don't learn the whole set faster, and remember it longer.

Subtraction: think addition

The best subtraction strategy is addition. To find 13 − 5, ask "5 plus what makes 13?" A child who knows 5 + 8 = 13 knows the answer. That's why the game puts subtraction facts on the same grid as the addition facts they undo, and why the Fact families game asks all four facts in a row.

Missing number questions build the same habit from the other side: 5 + □ = 13 is a subtraction problem in disguise. Many children find missing addends hard at first, which is a sign they're worth practicing.

A plan by grade

How to use the timer well

The What Works Clearinghouse practice guide for elementary math intervention recommends timed activities as one way to build fluency, rated as having strong evidence. But a clock helps only when a child can already find the answer. Keep young children in Practice, where there's no timer, until most of the grid is yellow or green. Then a daily 60-second Challenge, trying to beat their own best, gives them a reason to get faster. Best scores stay on your device and never go anywhere else.

If a child gets upset by the timer, drop it. Untimed practice with the adaptive schedule still builds fluency, more slowly.

Paper practice and next steps

Print a worksheet of just the facts your child still needs from the Learn tab or the results card. It opens our math worksheet generator with those facts filled in and an answer key. For a full sheet of mixed practice, try addition and subtraction worksheets or addition facts worksheets, and for hands-on work, our ten frame and number line show the make-ten strategy with counters and jumps.

When addition and subtraction are solid, move on to the times tables game, which uses the same engine for multiplication. To connect facts to real life, the counting money game turns adding into making change. Our math facts fluency guide explains how all four operations build on each other, and XtraMath, Mathseeds and SplashLearn, listed below, are full programs many families pair with free practice.