Ready to Print
This Subtraction Within 20 drill has 40 problems for Grade 1. Beach theme. Answer key included.
⬇ Download Free Math DrillGet new free worksheets every week.
All worksheets checked by our AI verification system. No wrong answers — guaranteed.
Max spotted 20 seashells washing away in the tide! He must subtract and save them before the waves disappear forever!
Standard: CCSS.MATH.1.OA.C.6
Preview
Page 1 — Drill
Page 2 — Answer Key
What's Included
About this Grade 1 Subtraction Within 20 Drill
Subtraction within 20 is a cornerstone skill that helps first graders understand how numbers relate to each other and build confidence with math in everyday moments. At ages 6 and 7, children are developing the mental flexibility to break apart numbers and visualize what happens when we take away—whether that's sharing snacks, removing toys from a pile, or counting down game turns. Mastering subtraction facts up to 20 strengthens a child's number sense, making it easier to solve word problems and prepare for addition and subtraction within larger numbers. When students can quickly recall facts like 15 − 7 or 13 − 6, they free up mental energy for more complex problem-solving. This drill builds automaticity—the ability to recall facts without counting on fingers every time—which is essential for success in second grade and beyond. Regular practice with these facts also helps children spot patterns (like how 10 − 3 and 15 − 3 are related) that deepen their mathematical thinking.
What your student will practice
- Recall subtraction facts with minuends up to 20 fluently
- Use strategies like counting back or using ten-frames to solve subtraction problems
- Apply subtraction-within-20 to solve simple word problems
- Recognize the relationship between addition and subtraction facts
Common mistakes to watch for
Many Grade 1 students confuse the order of numbers in subtraction and subtract the smaller from the larger number regardless of position—for example, answering 7 − 12 as 5 instead of recognizing it's impossible. Others count incorrectly when using the "counting back" strategy, losing track of how many they've counted down and landing on the wrong number. Some children also rely too heavily on finger counting and struggle when the minuend gets larger, since fingers alone become unreliable. To spot these errors, ask your child to explain their thinking: "How did you get that answer?" Watch whether they're using ten-frames or a number line to check their work, or if they're guessing.
Create a real-world subtraction game using small objects like blocks, crackers, or toy cars. Start with a pile of 12 to 15 items, then give simple directions: "We have 14 blocks. Take away 6. How many are left?" Let your child physically remove the objects and count what remains, then write the number sentence together (14 − 6 = 8). Rotate who gives the subtraction command so your child stays engaged, and gradually reduce the need to physically remove items as they build confidence with the facts.