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Estimation Station

Number · Year 1–Year 6

Guess how many are in the jar, then count them out in tens.

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About the estimation

A jar appears with something in it. The class estimates, and their guesses go on the number line under it: tap the line and a marker drops where you tapped, and it can be dragged. Three at once, so three children's guesses sit side by side and nobody has to remember whose was whose.

Then the jar is tipped out and counted. The pieces come out in hundreds first, then tens, then the ones left over, so the board reads "three hundreds, four tens and seven ones" and the total arrives at the end rather than at the start. The count out is the answer: there is no score, nothing flashes, and nobody is told they were close.

Three bands, up to 20, 100 and 500, cover estimating from Year 1 to Year 6. The jar is always full, so the clue is the size of what is in it rather than how high it comes up the glass, which is the same clue a real jar on a real table gives.

Every jar comes from a single number, which means the share button carries the jar itself. It also means there can be a jar of the day with nothing stored anywhere: press Today's and the number is worked out from the date, so every class in the country sees the same jar and it changes at midnight.

How to use it on your whiteboard

  1. 1Tap the number line to put an estimate on it. Tap it again for a second and a third, drag one to move it, and tap one to take it off.
  2. 2Press Count out. The pieces come out of the jar in hundreds, then tens, then ones, and the total appears once they have all landed.
  3. 3Press New for another jar, or Today's for the jar of the day, which is the same one in every classroom until midnight.
  4. 4Full of changes what is in the jar: sweets, cubes or beans.
  5. 5Tap Fullscreen to fill the board. Share copies a link with this exact jar in it.

Questions

Is there a jar of the day?
Yes. Press Today's and you get the jar of the day, which is the same jar in every classroom and changes at midnight. Nothing is stored and no account is needed: the jar is worked out from the date, so the link /tools/estimation?daily=1 opens it too and can go straight in a lesson plan.
How does it count them out?
In hundreds, tens and ones, arranged as hundred squares made of ten frames. A jar of 347 comes out as three full squares, four full frames and seven more, so the number can be read off the board rather than taken on trust.
Does it tell you whose guess was closest?
No. The answer goes on the line under the estimates and the class can see for themselves. There is no score and nothing that says well done, because the point is the estimating rather than the winning.
Do I need an account?
No. Trove Tools is free with no login, no subscription and no limits.