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This Subtraction Within 20 drill has 40 problems for Grade 1. Lavender Farm theme. Answer key included.
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Max discovered lost lavender bundles scattered everywhere! He must count and subtract quickly before the evening harvest ends.
Standard: CCSS.MATH.1.OA.C.6
Subtraction within 20 is a cornerstone skill that helps first graders develop number sense and build confidence with math. At ages 6-7, children are developing the cognitive ability to decompose numbers and understand that subtraction is the inverse of addition—skills essential for all future math learning. When your child can fluently subtract numbers up to 20, they're strengthening their mental math abilities and learning to think flexibly about numbers. This foundation makes word problems, money counting, and even sharing snacks at a lavender farm—or anywhere else—feel manageable rather than overwhelming. Mastery of subtraction within 20 also reduces cognitive load, freeing up mental space for more complex problem-solving. Students who practice these facts regularly develop automaticity, meaning they recall answers quickly without counting on their fingers, which is a key milestone for first grade.
Many first graders confuse the order of numbers in subtraction, writing or saying the answer to 15 - 8 as 7 when they meant 8 - 15. Another common pattern is counting incorrectly when "counting back"—they'll say "15, 14, 13..." but lose track of how many they've counted, landing on the wrong number. You might also notice a child starting from the wrong number or counting the starting number as the first count, which throws off their answer by one. Watch for hesitation or finger-counting on every problem; this signals they haven't yet internalized the facts and may need more concrete practice before moving to written drills.
Create a simple "subtraction game" using toys, blocks, or snacks your child enjoys. Show them a group of 12 items, hide some under a cloth, and have them figure out how many are missing. For example: "We had 12 crackers. Now I can see 7. How many are hiding?" This mirrors the concrete-to-abstract progression and makes subtraction feel like a puzzle rather than a worksheet task. Repeat with different numbers up to 20, and let your child do the hiding sometimes—it strengthens their understanding of the relationship between the numbers.