Max Rescues the Sandwich Shop: Subtraction Sprint!

About this Grade 2 Subtraction Within 20 Drill

Subtraction within 20 is a cornerstone skill that second graders need to build automaticity and confidence with numbers. At ages 7-8, children are developing the mental math strategies that will support all future math learning, from word problems to multi-digit computation. When students can quickly subtract numbers like 15 - 7 or 18 - 9 without counting on their fingers, their brains are freed up to focus on problem-solving and reasoning rather than calculation. This skill also connects directly to everyday situations—whether your child is figuring out how many cookies remain after sharing some with a friend, or understanding how much allowance they'll have left after buying a small toy. Fluency with subtraction within 20 also strengthens number sense, helping children understand how numbers relate to each other and building the foundation for understanding regrouping and larger subtraction problems in later grades.

What your student will practice

• Fluently subtract single-digit numbers from numbers within 20
• Use mental math strategies like counting back or making ten
• Solve subtraction word problems with numbers within 20
• Recognize the relationship between addition and subtraction facts

Common mistakes to watch for

The most common error second graders make is counting backward incorrectly when using the "count back" strategy. For example, when solving 14 - 3, a child might count "13, 12, 11, 10" and land on 10 instead of correctly landing on 11. Another frequent mistake is reversing the numbers—subtracting the larger number from the smaller (writing 7 - 15 instead of 15 - 7). Watch for students who still rely entirely on counting on fingers for every problem; this signals they need more guided practice with mental strategies. You'll also notice some children forget which number they're starting with and begin counting from zero instead of from the minuend.