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About this Grade 1 Adding Multiples Of 10 Drill

Adding multiples of 10 is a cornerstone skill that helps first graders develop number sense and mental math confidence. When children master 20 + 30 or 40 + 10, they're learning to think about numbers in groups rather than counting by ones—a huge leap in mathematical thinking. This skill directly supports their ability to add two-digit numbers later on and builds automaticity with tens, which is how our base-10 number system actually works. At ages 6 and 7, children's brains are developing stronger working memory, making this the ideal time to internalize these patterns. Real-world practice with multiples of 10 appears everywhere: combining toy collections, counting money, or organizing items in groups. Students who feel fluent with tens develop greater confidence and independence in math class, setting them up for success in addition, subtraction, and place value understanding throughout elementary school.

What your student will practice

• Fluently add two multiples of 10 up to 90 without counting by ones
• Recognize that 30 + 20 and 50 total the same number of tens
• Apply adding-multiples-of-10 to solve real-world story problems
• Explain addition of multiples of 10 using tens language (three tens plus four tens)

Common mistakes to watch for

The most common error is that first graders count by ones instead of by tens, turning 30 + 40 into a slow, error-prone process. Watch for students writing out tick marks or using fingers to count 1, 2, 3… rather than recognizing the pattern. Another frequent mistake is reversing digits: a child might say "30 + 20 equals 52" instead of 50, confusing the ones place. You can spot this by asking them to show you with tens blocks or to explain: "How many tens do you have altogether?" If they can't answer using tens language, they're likely still counting by ones underneath.