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This Subtraction Within 20 drill has 40 problems for Grade 1. Phoenixes theme. Answer key included.
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Max discovered 18 baby phoenixes trapped in ice caves! He must solve subtraction problems to melt the ice and free them before they hatch!
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 bridges concrete, hands-on math to more abstract thinking. At age 6-7, your child is developing number sense and learning that subtraction means "taking away" or "finding how many are left." This skill appears constantly in daily life: if you have 15 cookies and eat 3, how many remain? Mastering subtraction within 20 builds confidence and prepares students for larger numbers, word problems, and eventually two-digit computation. When children can quickly subtract numbers under 20, they develop mental math flexibility and strengthen their understanding of how numbers relate to each other. This is also when students begin internalizing fact families and recognizing patterns, which are essential for automaticity and problem-solving in later grades.
What your student will practice
- Subtract single-digit numbers from numbers 11-20 with fluency
- Solve "take away" and "how many left" subtraction scenarios
- Use counting back and known facts to find differences
- Recognize and apply subtraction patterns and fact relationships
Common mistakes to watch for
Many Grade 1 students count the starting number as they count backward, causing them to lose one from their answer. For example, when solving 14 - 3, they count "14, 13, 12" instead of starting at 13. You may also notice students mixing up which number to start with in a subtraction problem—they'll subtract the larger number from the smaller one. Another common error is losing track while counting on their fingers or using manipulatives, leading to answers that are off by one. Watch for hesitation or finger-counting on every single problem, which signals they haven't yet internalized basic facts.
Play a simple game at home using items your child loves—blocks, toy cars, or snacks. Start with a pile of 12-15 items and have your child physically remove a small amount while saying "I had 13, I took away 2, now I have 11." This real-world practice with concrete objects builds the mental image they need to eventually solve problems without manipulatives. Rotate who hides the items so your child practices both directions of thinking about the same subtraction fact.