Max Collects Fireworks: Fourth of July Math Rescue!

About this Grade 2 Adding Multiples Of 10 Drill

Adding multiples of 10 is a cornerstone skill that helps second graders recognize patterns in our number system and build mental math fluency. When children master 20 + 30 or 40 + 10, they're learning that the tens place does the real work—the ones place stays the same. This foundation makes larger addition problems feel manageable, since kids can break down numbers like 24 + 13 into (20 + 10) + (4 + 3). At ages 7–8, students are developing the abstract thinking needed to see numbers as groups of tens and ones rather than just individual dots or fingers. Whether they're counting money at a toy store or tracking points in a game like Fourth of July cornhole competitions, adding multiples of 10 appears constantly. Students who internalize this pattern gain confidence and speed that carries forward into subtraction, word problems, and eventually multiplication.

What your student will practice

• Recognize tens in two-digit numbers and isolate the tens place
• Add two multiples of 10 mentally without using manipulatives
• Apply adding multiples of 10 to solve simple word problems
• Explain why the ones place doesn't change when adding tens

Common mistakes to watch for

The most common error is students treating tens and ones as separate problems, writing 20 + 30 = 50 correctly but then getting confused and adding the ones digit too in a problem like 23 + 30, incorrectly arriving at 53 instead of 53. Another frequent mistake occurs when children forget that 10, 20, 30 have a zero in the ones place and try to 'add' that zero into their answer. Watch for hesitation or finger-counting in problems like 40 + 20—this signals the student hasn't grasped that 4 tens + 2 tens = 6 tens yet. You can spot this by asking them to show the tens using tally marks or drawings; if they struggle, they need more concrete practice before moving to abstract notation.