Flip a coin 20 times
You will flip a coin twenty times and record the split between heads and tails. Equal chances do not promise equal counts in one short run.
- Maths
- Starter
- About 15 minutes
Grown-up needed: yes for setup, checking and any preparation of paper or small items
What you need
- One coin selected by a grown-up
- Paper
- A pencil
- A low tray
The rule
Tally every flip.
How to do it
- Draw columns for heads and tails.
- Write your predicted split for twenty flips.
- Ask a grown-up to demonstrate a gentle flip above the low tray.
- Record one tally immediately after every landing.
- Stop when the combined tally reaches twenty.
- Compare your prediction with the two counted totals.
Why it works
For a fair coin, heads and tails have equal probability on each independent flip. That does not make the next result compensate for what happened before. A run of several heads can occur without changing the next flip’s chance. Over many trials the proportions often settle closer to one half, but no finite run must be exactly balanced. Your twenty-flip record is one sample that can differ from a partner’s equally fair sample.
Make it harder
- Repeat another twenty flips separately.
- Combine two recorded runs and compare proportions.
- Explain why a run of heads does not make tails due next.
Ask Taz
- Why can equal chances produce unequal counts?
- Why is tails not owed after several heads?
- Why do larger samples often give closer proportions?
For grown-ups
Stay with the coin and keep it away from younger children. Recording after each landing prevents the chart from depending on memory. Discuss variation rather than calling a prediction lucky or clever. Ask at dinner: “If we repeated the whole experiment, which details would stay the same and which could change?”
Taz is an AI and can be wrong, so stay close by. Read how safety works on Taz.
Show us yours
Film your hands and what you made, not your face or name. Ask a grown-up before posting anywhere else.
Questions parents ask
How much preparation does this need?
Use the household items above and begin with one small example. A grown-up can prepare the space or checking sheet while the child chooses the prediction. The time is an estimate and includes a little room to repeat.
What if we get different answers?
Compare the rule, the method and what each person recorded. A difference can reveal a changed assumption or an ordinary variation, so check before deciding someone must be wrong.
Does the child have to share online?
No. Discuss the work at home first. Public sharing is optional and needs the grown-up permission and privacy wording above.
More to try
See all Taz Challenges, or look through the science labs. One place for every why. Ask for early access at aitaz.com
Try it in 3D: Probability.