wunder beta

🔢 Addition and Subtraction Within 1,000

Use blocks, drawings, and place value to add and subtract three-digit numbers, jump by hundreds in your head, and get lightning-fast with facts up to 20.

3
lessons
~30 min
to learn
🔢 Math
subject
Ages 6–12
level
Start the course →

What you’ll learn

  1. Three-Digit Numbers With BlocksAdd and subtract within 1,000 using base-ten blocks and drawings, composing and decomposing when needed.Three-digit numbers are hundreds, tens, and ones (245 = 2 flats, 4 rods, 5 cubes). Add each place and compose a ten when the ones pass 9 (156 + 128 = 284); subtract each place and decompose a ten when the top digit is too small (243 − 118 = 125). Drawings make it visible.
  2. Lightning Facts to 20Recall all addition and subtraction facts within 20 quickly, using make-ten and fact families.Facts to 20 should be automatic. If one feels slow, make ten (8 + 7 = 8 + 2 + 5 = 15). Every addition fact hides subtraction facts in the same family: 8 + 7 = 15 means 15 − 8 = 7 and 15 − 7 = 8. Practice makes them lightning fast.
  3. Jumping by HundredsMentally add and subtract whole hundreds to and from three-digit numbers.Adding or subtracting whole hundreds changes only the hundreds digit — the tens and ones stay put. 345 + 200 = 545 and 762 − 400 = 362. Thinking in hundreds makes big mental jumps quick and reliable.

Questions this course answers

In the number 245, what is the value of the 2?

The 2 is in the hundreds place, so it means 200.

What is 156 + 128?

Ones 6 + 8 = 14 (compose a ten), tens 5 + 2 + 1 = 8, hundreds 1 + 1 = 2, giving 284.

In 243 − 118, why do you decompose a ten?

The ones digit 3 is smaller than 8, so you break a ten into ten ones to make 13 − 8.

If 8 + 7 = 15, what is 15 − 8?

Addition and subtraction are linked: since 8 + 7 = 15, then 15 − 8 = 7.

What is 345 + 200?

Add 2 hundreds to the 3 hundreds; the 45 stays: 545.

What is 762 − 400?

Take 4 hundreds from 7 hundreds to leave 3 hundreds; the 62 stays: 362.

Grounded in trusted sources

  • Khan Academy Kids
  • PBS Kids — early math
  • NAEYC — early math learning
  • Britannica Kids

Every Wunder lesson is built from real, reputable sources — never invented.

Related Math courses

🔍Checking Answers by Rounding🧹Collecting Like Terms📍Coordinates in All Four Quadrants🐇Counting On and Counting Back🎯Estimating and Checking Answers❓Finding the Missing Number🔗Generating Sequences📈Graphing Equations

Wunder is a personalized learn-anything platform — tell it any topic and it builds a beautiful, fact-checked course in minutes, with narration, a knowledge check, and a college-style University track.

Browse more Math courses · All topics · Home

© 2026 Wunder Learning LLC · Terms & Privacy