A box contains 90 discs numbered from 1 to 90. If one disc is drawn at random from the box, what is the probability that it bears a perfect square number?
Answer and explanation
Correct answer: A. 1/10
- Step 1: Perfect squares between 1 and 90 are: 1, 4, 9, 16, 25, 36, 49, 64, 81 (9 numbers: 1^2 to 9^2).
- Step 2: Total possible outcomes = 90.
- Step 3: Probability = 9 / 90 = 1/10.
Why not the others: Other values result from miscounting the favorable outcomes in the sample space, inverting the probability fraction, or confusing independent with mutually exclusive events.
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