Second Grade · Math · week 5

Expanded form

Write 3-digit numbers in expanded form as the sum of hundreds, tens, and ones.

Expanded form breaks a number into the value of each place, added together. 452 becomes 400 + 50 + 2 -- you can see exactly what each digit is worth.

Expanded form is the opposite of standard form. Standard form is the short way (452); expanded form is the long way that shows the parts.

📋 For the teacher
Teach it (10–15 min):
  • Have them build the number with blocks first, then write the matching expanded form -- the blocks and the plus-sign form should match exactly.
  • Accept "200 + 8" or "200 + 0 + 8" for a number with zero tens -- both are correct.
  • Practice going both directions: standard to expanded, and expanded back to standard.
  • Ask them to say each part out loud as they write it: "seven hundred, plus thirty, plus six."
Talk about it:
  • Why is expanded form useful for understanding a number?
  • What happens to expanded form when a place has a zero?
  • Can you turn 800 + 20 + 1 back into standard form?

Mastery looks like: They convert confidently between standard and expanded form for any 3-digit number.

Common stumbles: Writing the wrong number of zeros on a place value (writing 5 instead of 50); dropping a place instead of using zero.

See it visually

Interactive, spoken-aloud tools that show this idea in motion.

Place ValueWatch ones, tens, hundreds, and thousands build big numbers.try →AdditionSee groups combine — with counters, blocks, and the number line.try →
Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Math for this learner.
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