Max Discovers the Science Fair Volcano: Add by Tens!

About this Grade 2 Adding Multiples Of 10 Drill

Adding multiples of 10 is a cornerstone skill that teaches second graders how numbers work in groups, setting them up for multiplication, place value mastery, and mental math fluency. At ages 7–8, students are developing their ability to recognize patterns and work with tens—the building blocks of our base-10 number system. When a child can quickly add 20 + 30 or 50 + 40, they're not just practicing addition; they're learning that we can break apart numbers into chunks and recombine them, a strategy that will serve them through division, fractions, and algebra. This skill also builds confidence with larger numbers and reduces anxiety around math. In real life, kids use this when counting money in dimes, keeping score in games, or organizing items for a science fair project into groups of ten. Fluency with multiples of 10 also frees up mental energy so students can focus on more complex problem-solving rather than struggling with basic facts.

What your student will practice

• Identify and recognize multiples of 10 up to 100
• Add two multiples of 10 mentally without counting by ones
• Apply adding-multiples-of-10 to solve word problems with groups of tens
• Explain their thinking by showing tens as units rather than individual ones

Common mistakes to watch for

Many second graders forget to count by tens and instead revert to counting by ones—so 20 + 30 becomes a slow count of 1, 2, 3... up to 50 instead of thinking "2 tens plus 3 tens equals 5 tens." Another common error is dropping the zero; students might write 2 + 3 = 5 when working with 20 + 30, losing track of place value entirely. You'll spot this when a child writes the answer as a single digit or pauses to count on their fingers for every problem. The fix is to explicitly model tens as units—use groups of ten objects or draw ten-frames—so students see 20 + 30 as "20 and 30" (not twenty individual items), making the pattern clear.