The Sharing Jar — Make It Fair (Find the Missing Number)
A jar of moon-beads spills, and Pim and Bo scoop up different amounts — one jar glows full, the other goes quiet. Help make it fair: work out how many more beads the quiet friend needs and say that number, then watch the beads float over and two friends lean their heads together. A warm Grade-1 missing-number game aligned to Common Core 1.OA.D.8.
A jar of moon-beads spills, and Pim and Bo scoop up different amounts — one jar glows full, the other goes quiet. Help make it fair: work out how many more beads the quiet friend needs and say that number, then watch the beads float over and two friends lean their heads together. A warm Grade-1 missing-number game aligned to Common Core 1.OA.D.8.
About this activity
Pim and Bo scoop moon-beads into their jars at The Sharing Jar, and one jar always ends up fuller — so the child finds the missing number that makes it fair: how many more the quiet jar needs, how big the gap is, or how many there were to start, tapped on tiles from 0 to 10. It's a free Grade 1 math activity that runs in the browser with no account.
The numbers stay small, but the unknown moves around — sometimes it is the amount to add, sometimes the difference, sometimes the starting amount that has to be uncovered. That is the whole point: the child is not just adding two numbers, but figuring out which part is missing and how to find it, using counting-on and fact-family thinking. Saying the number out loud before tapping it ties the spoken answer to the written numeral.
It is aligned to Common Core 1.OA.D.8 — finding the unknown number in an addition or subtraction situation, in any position. No timer, no score — just calm, playful practice.
What's inside this activity
- Designed for Grade 1 learners (ages about 6–7)
- Common Core strand: Operations & Algebraic Thinking
- Aligned to Common Core standard 1.OA.D.8
How to play
Read the two jars and the question — how many more beads does the quiet friend need to be fair?
Work it out, say the kind number, then tap that numeral on the tiles from 0 to 10 and press Check.
Not quite? Try again as many times as you like — there is no timer and no score.
What your child practices
- Find the missing number when the unknown is the part to add, the difference, or the start
- Use counting-on and fact families to make two amounts equal
- Work out how much more one group has than another within 10 and a little beyond
- Connect a spoken number to the written numeral by saying it before tapping
Learning goals
Find the unknown number in an addition or subtraction story — the focus of Common Core 1.OA.D.8.
Understand that the missing part can sit anywhere — the sum, an addend, or the starting amount.
Build the equal-and-fair number sense that early addition and subtraction depend on.
Frequently asked questions
- What does the The Sharing Jar — Make It Fair (Find the Missing Number) activity teach?
- The Sharing Jar — Make It Fair (Find the Missing Number) is a free interactive activity for Grade 1, focused on Operations & Algebraic Thinking. Children play it right in the browser — no printing, login, or setup required.
- Is The Sharing Jar — Make It Fair (Find the Missing Number) free to use?
- Yes. The Sharing Jar — Make It Fair (Find the Missing Number) is completely free, with no signup and no paywall, on any tablet, laptop, or classroom whiteboard.
- Which ages is this activity for?
- It is designed for Grade 1 (Operations & Algebraic Thinking) and works well for whole-class, small-group, or independent practice.