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This Subtraction Within 20 drill has 40 problems for Grade 1. Helicopters theme. Answer key included.
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Max's helicopter rescue team has 18 stranded pilots—he must solve subtraction problems to bring each one home safely!
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 counting and abstract number sense during first grade. At ages 6-7, children are developing the mental flexibility to understand that numbers can be broken apart and recombined—a foundation for all future math. When your child can quickly solve problems like 15 - 3 or 18 - 5, they're building number fluency that makes word problems, money handling, and real-world decision-making feel natural rather than overwhelming. This skill also strengthens working memory and logical thinking, as students learn to visualize groups of objects even when they can't physically see them. Mastering subtraction within 20 typically happens through repeated, varied practice that moves from using manipulatives to mental math. Students who develop confidence here often approach harder math with less anxiety and greater independence.
What your student will practice
- Subtract single-digit numbers from teen numbers using objects or drawings
- Recognize and use the relationship between addition and subtraction facts
- Solve subtraction word problems with numbers up to 20
- Fluently recall basic subtraction facts within 10 to build automaticity
Common mistakes to watch for
The most common error is counting backward incorrectly when students try to use the 'count on' strategy in reverse—for example, saying 15 - 3 = 11 because they count back but skip numbers or lose track. Another frequent mistake is confusing which number to start with, especially in word problems; a child might solve 'There are 17 apples. 6 are eaten. How many are left?' by subtracting the larger from smaller (6 - 17) instead of recognizing that 17 is the starting amount. Watch for students who write the answer before actually solving, copying from memory rather than calculating. You'll spot these errors when the child hesitates, uses fingers inconsistently, or gives answers that don't match their manipulatives.
Create a simple subtraction game using household items like cereal pieces or crackers during snack time. Place 12 items on a plate and say, 'We have 12 crackers. If you eat 4, how many are left?' Let your child remove the 4 pieces and count what remains, repeating with different starting numbers. This real-world, edible context makes subtraction concrete and memorable for six-year-olds, and the repetition builds automaticity faster than worksheets alone. The tactile and gustatory elements stick in their memory much longer than abstract symbols.