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This Subtraction Within 20 drill has 40 problems for Grade 1. Photography theme. Answer key included.
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Max's camera film scattered everywhere! He must subtract to find all 20 photos before the photo shoot ends!
Standard: CCSS.MATH.1.OA.C.6
Subtraction within 20 is a cornerstone skill that helps six- and seven-year-olds build number sense and mental flexibility. At this age, children are developing the ability to decompose numbers and understand that subtraction is the inverse of addition—skills they'll rely on for multiplication, division, and word problem-solving in later grades. When your child can quickly solve problems like 15 − 7 or 13 − 5, they're strengthening working memory and building confidence with abstract thinking. These fluency skills also connect directly to daily life: making change, sharing toys fairly, or figuring out how many snacks are left. Most importantly, mastering subtraction within 20 gives children a secure foundation so they can tackle larger numbers without anxiety and develop genuine mathematical thinking rather than memorization.
Many Grade 1 students count forward instead of backward when subtracting, especially when the minuend is larger—they'll count up from 7 to solve 15 − 7 instead of counting back from 15. Others lose track of their count or skip a number, arriving at an incorrect answer by one or two. Some children also confuse the order of numbers and solve 7 − 15 when the problem shows 15 − 7. Watch for hesitation or finger-counting on every single problem, which signals the child hasn't internalized foundational facts and may benefit from more skip-counting practice or ten-frame work.
Play a real subtraction game at home using a small pile of objects—snacks, blocks, or toy animals work perfectly. Place 12 items in front of your child, then ask, 'If you eat 4, how many are left?' Let them physically remove the items and count what remains. Rotate who hides the objects so your child has to figure out the subtraction fact from the result. This concrete, playful approach mirrors a photographer framing and refocusing a shot—your child is actively building the mental image of how numbers decrease. Do this for 5–10 minutes, a few times a week.