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About this Grade 3 Mixed Add Subtract Drill

By third grade, students need to move beyond simple addition or subtraction problems and tackle mixed operations in a single problem. When your child solves something like 23 + 15 - 8, they're building the mental flexibility to hold multiple steps in their working memory, switch between operations, and track their progress toward a final answer. This skill is foundational for multi-step word problems they'll encounter throughout elementary school and directly supports algebraic thinking later on. At ages 8-9, children's brains are developing the executive function to plan ahead and self-check their work, making this the ideal time to strengthen these habits. Practicing mixed-add-subtract drills also builds automaticity with two-digit numbers, so students can focus on the logic of the problem rather than struggling with basic facts. Real-world situations—like combining game scores, calculating money for a snack purchase, or adjusting ingredient amounts while cooking—all require this flexible thinking.

What your student will practice

• Solve two-digit mixed-add-subtract problems without regrouping
• Identify and apply the correct operation in sequence left to right
• Check answers using inverse operations or alternative strategies
• Explain reasoning for each step in a two-operation problem

Common mistakes to watch for

Many third graders either ignore the second operation entirely (solving only the addition, for example) or reverse the order and subtract first. Watch for answers that seem too large or too small compared to the starting number, or students who write down only one intermediate step. Another common error is treating subtraction as addition—for instance, calculating 40 + 12 - 5 as 40 + 12 + 5. Ask your child to point to each operation symbol before solving and to say the operation aloud ("add, then subtract") to catch these habits early.