Max Rescues Penguin Pups: Arctic Subtraction Sprint!

About this Grade 1 Subtraction Within 20 Drill

Subtraction-within-20 is a foundational skill that helps first graders make sense of the world around them—from sharing snacks with friends to figuring out how many crayons are left in a box. At ages 6-7, children are developing the mental flexibility to break numbers apart and understand that subtraction is the opposite of addition. Mastering these problems builds number sense, which is the ability to think flexibly about quantities and relationships between numbers. This skill is essential because it prepares students for two-digit subtraction, word problems, and real-world math reasoning. When children can fluently subtract within 20, they develop confidence in math and strengthen their working memory. These drills help cement automaticity—the ability to solve problems quickly without counting on fingers—so their brains are free to tackle more complex math concepts later.

What your student will practice

• Solve subtraction problems with numbers 0-20 accurately and with increasing speed
• Recognize subtraction as taking away or finding the difference between two numbers
• Use mental math strategies like counting back or using number bonds to solve efficiently
• Apply subtraction skills to simple real-world situations and story problems

Common mistakes to watch for

Many first graders confuse the direction of subtraction—they may reverse the numbers or count up instead of counting back. For example, with 15 - 3, a child might accidentally solve 3 - 15 or count up from 3 to 15 instead of back. Another common error is losing track while counting on fingers, especially with larger numbers, leading to answers that are off by one or two. Watch for students who write down random answers without a strategy, which signals they don't yet understand what subtraction means rather than just needing practice.