Unit 4 · Statistics and Probability
Marble Bag — Which Probability Statement Is True?
Lesson 2 of 8
Bag-of-marbles probability always starts the same way: write each colour as a fraction over the total, then check every statement on its own before you pick an answer.
Three-statement probability items appear throughout Selective MR — students who convert to fractions immediately avoid the intuition traps on “equally likely” claims.
The examiner checks whether you compare probabilities with the same denominator, spot false equalities, and do not confuse “greater than” with “equal to”.
A bag lists counts for several colours. Three claims compare probabilities (greater than, equal to, etc.). You identify which claims are true.
Best approach: Total = sum of all counts. For each statement, write P(event) = favourable ÷ total. Compare numerators when denominators match. Only then choose the option that lists the correct statements.
Question
A bag contains 18 marbles:
- 7 red
- 5 blue
- 4 green
- 2 yellow
One marble is picked at random. Three statements are made:
-
The probability of picking red is greater than picking blue.
-
The probability of picking green equals the probability of picking blue.
-
The probability of picking yellow is greater than picking green.
Which statement(s) are correct?
Select an answer to see the explanation.
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