Simple Chance Experiments · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Doing a chance experiment

Mathematics · Probability · ages 9-10
Name ______________________   Date ____________

  1. You flip a fair coin 20 times. About how many heads do you expect?

    • About 10
    • All 20
    • None at all
    • Exactly 20 tails

  2. Maya says flipping a coin 20 times and tallying heads and tails is a chance experiment. Is Maya right?

    Circle one:   True   False

  3. You flip a coin. What are the two possible results?

    • Heads or tails
    • Odd or even
    • Win or lose

  4. If you roll a die many times, each number should come up about the same number of times as the others.

    Circle one:   True   False

  5. Sam rolled a die 30 times and got the number 3 nine times, more than the 5 he expected. What's the best way to think about this?

    • Sam must have counted wrong
    • The die will always land on 3 now
    • Real results can land higher or lower than expected by chance

  6. Heads came up 11 times in 20 flips. How many tails came up?

    Answer: ______________

  7. You roll a die 30 times and get five 6s. What does this result suggest?

    • The die must be unfair
    • About what was expected, since 30 shared by 6 faces gives 5 each
    • Sixes never come up on a fair die
    • You should always get exactly five 6s

  8. A class rolls a die 30 times. About how many times would they expect the number 5 to come up?

    • 5
    • 6
    • 30

  9. Leo flips a coin 5 times and gets 5 heads in a row. He says the coin must be broken. What's the best explanation?

    • Heads and tails must always alternate
    • A small experiment can show an unusual streak by chance
    • The coin is definitely unfair

  10. Sofia says drawing counters with eyes closed keeps the experiment fair. Is Sofia right?

    Circle one:   True   False

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Doing a chance experiment W1-mt_J4j7d3iAfg-s1

  1. About 10 · Halves of 20 is 10, so about 10 heads.
  2. True · Maya is right: repeated flips with recorded outcomes are exactly that.
  3. Heads or tails · A coin has two sides, heads and tails, so every flip lands on one of those two.
  4. True · A die has six equally likely sides, so over many rolls each number tends to show up about as often as the rest.
  5. Real results can land higher or lower than expected by chance · Actual results bounce above and below what you expect, especially with a small number of rolls.
  6. 9 · 20 - 11 = 9.
  7. About what was expected, since 30 shared by 6 faces gives 5 each · Five 6s matches the expected 30 / 6 = 5.
  8. 5 · There are six numbers on a die, so 30 rolls split evenly gives about 5 rolls for each number.
  9. A small experiment can show an unusual streak by chance · With only a few flips, streaks happen sometimes. Flipping many more times would likely show a more even mix.
  10. True · Sofia is right: blind draws stop peeking from skewing results.
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