Free odd and even games with counter pairs
A whole number is even when its counters can be arranged into pairs with none left over. An odd number leaves one counter without a partner. Odd and Even Workshop connects that idea to number sorting: explore counters from zero to twenty, then sort numbers in three ranges. There is no timer, automatic sound, compulsory dragging or account requirement.
Make pairs and see the remainder
Open Explore counter pairs and choose a whole number from 0 to 20. Make a pair moves two loose counters into a visible group. Keep making pairs until zero or one counter remains. Undo a pair returns two counters; Separate all pairs restores the loose set. Changing the number starts that set unpaired. The chosen number and number of pairs save separately from your sorting boards.
Seven makes three pairs and leaves one over, so seven is odd. Eight makes four complete pairs, so eight is even. Zero is even too: it has no unpaired counter, and 0 = 2 × 0. The explorer uses counters rather than a timed question so you can compare neighbouring numbers and explain the change.
Sort eight numbers at a time
Choose a range: 0–20, 0–100 or 0–1,000. Each collection has six boards, each containing eight distinct whole numbers: four odd and four even. Numbers may appear again on other boards, especially in the smallest range. Board one includes zero and the range’s upper boundary. The boards are fixed practice sets; replay does not pretend to generate a different challenge.
Select a numbered tile, then choose Place in Odd or Place in Even. Its group remains written on the tile. Select it again to move it, or unsort the selected number. Undo last move reverses up to 24 moves, including Unsort all numbers. Check my sorting checks the entire board, reports unassigned and incorrectly grouped numbers, and keeps your work so you can correct it. A matched board stays visible until you choose the next unfinished board.
Use pairs or the final digit as working
Show working provides optional support for a selected number. Up to twenty, it shows the complete pairs and any counter left over. Larger values are split into groups of ten and their final digit. Each ten makes five complete pairs, so the final digit determines whether anything remains unpaired. For example, 137 = 130 + 7: thirteen tens make complete pairs, while the final seven leave one over. Therefore 137 is odd.
Whole numbers ending in 0, 2, 4, 6 or 8 are even. Those ending in 1, 3, 5, 7 or 9 are odd. The activity does not cover negative numbers or decimals. Working is available without a penalty; collection stickers recognise completed practice, including practice with help, rather than independent mastery.
Saved boards, replay and collection stickers
Each board keeps its assignments, undo history and checked state in this browser on this device. You can choose any board without unlocking earlier ones. All six boards in a range earn its collection sticker: three stickers in total. Practising again retains completed-board records and previously saved stickers. Restart asks before replacing unfinished sorting; clearing a board is reversible with Undo.
Puzzle progress and sticker saving are checked separately. A saved-sticker message requires the matching sticker to be read back. If storage fails, you can keep playing, but leaving or refreshing may lose work; check the sticker book when reward saving cannot be confirmed. A different browser or cleared storage starts fresh. There is no cloud save claim.
Touch, mouse and keyboard
No dragging is required. Select a number with a tap, click or native keyboard activation, then choose its named group. Focus moves to the Odd destination after selection and to the next unassigned tile after placement. Tab reaches Even and the other controls. Enter and Space activate once; holding them does not rapidly place numbers or advance boards. Both group names remain visible, so colour is not the only cue.
For a larger view of number patterns, paint or highlight odds, evens and multiples in the Hundred Square. Build equal groups and connect pairs to addition in Doubles Workshop, or explore equal sharing in Division Workshop.