Max Conquers the Karate Dojo: Subtraction Sprint!

About this Grade 1 Subtraction Within 20 Drill

Subtraction-within-20 is a cornerstone skill that helps six- and seven-year-olds build number sense and flexible thinking about quantities. At this age, children are developing the ability to break apart numbers and understand that subtraction is the inverse of addition—skills they'll use every day, from sharing snacks with classmates to figuring out how many crayons are left after using some. Mastering these problems strengthens their mental math fluency and sets a solid foundation for multi-digit subtraction and word problems later. When students can quickly subtract within 20 without counting on their fingers every time, their working memory is freed up to tackle more complex math thinking. This worksheet targets the specific range where students transition from concrete manipulatives to visualizing the math in their heads, a critical developmental leap in first grade.

What your student will practice

• Solve subtraction problems with answers 0 to 20 fluently
• Recognize and use the relationship between addition and subtraction facts
• Use strategies like counting back, counting up, or thinking of ten to solve efficiently
• Represent subtraction situations with pictures, objects, or number sentences

Common mistakes to watch for

First graders often count backward incorrectly when solving problems like 14 − 3, losing track of how many steps they've taken or landing on the wrong number. Another frequent error is confusing which number to start with—some students subtract the larger number from the smaller one without understanding order matters (writing 5 − 12 instead of 12 − 5). Watch for students who still rely entirely on fingers and cannot visualize the problem, as this suggests they need more concrete practice before moving to abstract notation.