Preview · the opening missionRead this to the class:
At the school fair, the "Red Wins" stall has four bags of counters. You pick one bag, reach in without looking, and if you pull out a red counter, you win a prize. Max says, "I'll pick bag D. It has 7 red counters, more than any other bag." His friend isn't sure. Your team's job: work out which bag gives the best chance of winning, test it, and advise the next person in line.
Teams of three, with jobs that rotate after each bag: Drawer (draws one counter without looking), Shaker (shakes the bag and puts the counter back), Recorder (tallies red and blue).
Look inside the PDF
Sample pages, stamped “preview”. The download is the clean, full lesson.
In the full lesson PDF
8 printable pages
- Predict (5–10 min)
- Hunt (20 min)
- Reveal (10–15 min)
- Act (10 min)
- Background for the teacher
- Assessment
- Student sheet
- Worksheet: Label it
- Worksheet: Try it at home
On the student sheet
- My prediction
- Working it out
- Testing it: 20 draws per bag, with replacement
- What did we find?
- Our advice
- Exit ticket
- Label it
- Try it at home
US Letter, prints cleanly in black and white. The student sheet is on its own page, ready to photocopy.
Free with an account (any 3 lessons), or US$19 for all 4 lessons in this unit.
What students show by the end
- Finds theoretical probability
- Compares probabilities
- Uses the complement
From the lesson’s rubric, which scores each one as not yet, getting there or got it.
Questions teachers ask
How long does “Which bag would you pick from?” take?
50–60 min. Group size: teams of 3.
How much prep does it need?
15 minutes: make four bags (paper bags or envelopes you can't see into) for each team, or one set of four bags passed between teams. Bag A: 3 red and 2 blue. Bag B: 5 red and 5 blue. Bag C: 6 red and 4 blue. Bag D: 7 red and 8 blue. Counters, cubes or paper squares all work if they feel the same. Label the bags A to D.
What materials do I need?
Counters or paper squares, red and blue, that feel the same; paper bags or envelopes. Cost: free with counters or cut paper squares in two colours.
Which curriculum standards does it cover?
Common Core Math (US): 7.SP.C.5, 7.SP.C.6 and 7.SP.C.7 (partly).
What’s in the lesson PDF?
A teacher guide that walks you through predict, hunt, reveal, act, background for the teacher and assessment, then a student sheet (“My prediction”; “Working it out”; “Testing it: 20 draws per bag, with replacement”; “What did we find?”; “Our advice”; “Exit ticket”; “Label it” and “Try it at home”) on its own page, ready to photocopy. It’s US Letter and prints cleanly in black and white.
Can I try it for free?
Yes. A free account includes any 3 full lessons of your choice, and this can be one of them. After that, this unit is US$19 for all 4 lessons, yours to keep, or every lesson is US$199 a year.