Estimation Jar
A jar fills with a random number of dots for a quick timed peek, then hides again. Collect names and guesses, then run a drumroll reveal that shows the true count and closest guesser.
Built by the AbraCalc team
How to play
- Set the fewest and most dots the jar could hold, then tap Fill the Jar.
- Tap Peek to reveal the jar for 3 seconds; peek again as many times as you like.
- Type each student's name and guess, tapping Add Guess after every one.
- Tap Reveal Count for a drumroll, then see the true count and the closest guess.
Set a range for how many dots the jar might hold, then tap Fill the Jar to randomly fill it within that range. Students get a timed 3-second peek at the jar, just long enough to form an estimate without being able to carefully count every dot. Add each guesser's name and number as they call them out, building a visible list on screen. When everyone has guessed, tap Reveal Count for a short drumroll before the true number appears along with whoever guessed closest. It is built for the classic estimation-jar routine used to build number sense, encourage reasoning about quantity, and spark discussion about strategies like grouping and benchmarking, all without any physical jar or counting by hand.
Frequently asked questions
- How long does each peek last?
- Each peek shows the jar for exactly 3 seconds before it covers back up, which is enough time to form an estimate but not enough to carefully count every dot one by one.
- Can students peek more than once?
- Yes, tap Peek as many times as you like before guessing; each peek is a fresh 3-second look and the dot count never changes between peeks.
- How is the closest guess picked?
- The tool compares every submitted guess to the true dot count and highlights whichever guess has the smallest difference, with ties going to whoever guessed first.