Track / Stage 4 / 211 of 340 #471 of 1964

G1.4 16 cards are marked from 1 to 16 and one is drawn at random. If the chance of it being a perfect square number is $\frac{1}{d}$, find $d$.

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Official solution

Perfect square numbers are $1,4,9,16$.
$$\begin{array}{l} \text { Probability }=\frac{4}{16}=\frac{1}{d} \\ d=4 \end{array}$$

Source: NuminaMath-1.5, licensed Apache-2.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.