Numbers & Place Value

Explore large and small numbers and discover how place value works – interactively. This is not a drill app but an open environment for exploring and experimenting.

Understanding place value is one of the most important foundations in mathematics: it underpins mental and written calculation strategies, decimals and much more.

HOW IT WORKS
Drag the digits up and down with your finger. Go beyond 9 and watch ten items bundle into one item of the next place. Go below 0 and see how the next place is "unbundled".

Swipe or tap the quantity below a digit to change it.

At the bottom of the screen, choose how the quantity is shown: place value counters, base-ten (Dienes) blocks, euro money, dot fields, 3D base-ten material and more.

TOOLS ON THE RIGHT
- Speaker: listen to the number being read aloud.
- Speech bubble with check mark: read the number aloud yourself and check whether you read it correctly.
- Expand: shows, for example, 142 as 100 + 40 + 2.
- Dice: roll a random new number.
- Speech bubble with dots: say a number and watch it appear.
- Question mark: some places are covered, the number is read aloud and you fill in the missing digits.

MORE OPTIONS
- Use the grey arrows to add or remove places – explore numbers up to 100 trillion.
- Move the decimal point to work with decimals down to millionths.
- Tap a place label (O, T, H …) to change its color.
- Swipe across a digit to cover it; tap the cover to enter your answer and get feedback.
- Number words above the digits in matching place colors – optionally as "Say Ten" number words (e.g. 284 = "two hundred eight ten four").
- Many settings in the app: thousands separator, place labels, speech rate, show or hide tools and representations, protect settings.
- Share a setup or task with your class via QR code.
- English (UK/US) and German.
- Also available in the browser: zahlen.urff.app

IDEAS FOR THE CLASSROOM
- Number dictation: show 3,469.
- Keep adding one to the ones. What happens when you go past 9?
- Show 340. What happens when you take one away from the ones? What about 300?
- Show 5,216 and expand it: which numbers make it up (5,000 + 200 + 10 + 6)? What about 5,316?
- Listen to a number, then change one place. Can you read the new number correctly?
- Tap the question mark and solve some tasks – the app counts them for you.
- Why does the leading zero in 0453 disappear? Why does the zero stay in 204 or 240?