EN
BuilderGrade 7⏱ 20 min

Probability

Flip coins, roll dice and spin a spinner hundreds of times, and watch the results settle toward the probability.

Standards: 7.SP.C.57.SP.C.67.SP.C.7

1Wonder

You flip a coin 10 times and get 7 heads. Is the coin unfair, or was that just luck? How could you find out?

2Explore

Chance machine

This activity needs a bigger screen

Turn your phone sideways, or open this lesson on a tablet or computer. The explanation and quiz below work here.

No tries yet. Press a button!00.250.50.751heads1/2tails1/2SillyChili
What to use
Try it
Try this
  • Flip the coin 10 times. Is the share of heads exactly 0.5? Now press ×100 a few times. What happens to the bars?
  • Roll the die many times. Which number comes up most? Do the bars get closer to the dashed lines?
  • Spin the spinner. Why does red come up about half of the time?
  • Press Clear results and try again. Do you get the same numbers?

3Explain

0impossible¼unlikely½even chance¾likely1certainSillyChili
Step 1 of 5

A number from 0 to 1

The probability of an event says how likely it is. 0 means it can never happen, 1 means it is certain, and ½ means it is just as likely to happen as not.

ProbabilityP(event)=favorable outcomesall equally likely outcomesP(\text{event}) = \frac{\text{favorable outcomes}}{\text{all equally likely outcomes}}

It is always between 0 and 1. In a few tries anything can happen; in many tries the results get close to the probability.

4Practice

Question 1 of 5

What is the probability of rolling a 3 on a fair die?

5Recap

  • Probability is a number from 0 (impossible) to 1 (certain).
  • For equally likely outcomes: P = favorable ÷ all outcomes.
  • Experimental probability comes from real tries; it varies a lot in small samples.
  • With many tries it gets close to the theoretical probability.