Consider a deck of cards. If you draw a single card, what is the probability that you draw a king or a queen

解

C o n s i d er a d ec k o f c a r d s . I f yo u d r a w a s in g l e c a r d, w ha t i s t h e p ro babi l i t y t ha t yo u d r a w a kin g or a q u ee n

\frac{2}{13}

十進法表記

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解答ステップ

Find the probability of you draw a king:

\frac{1}{13}

Find the probability of a queen:

\frac{1}{13}

Since the events are disjoint, Use the formula

P (X_{1} \lor X_{2} \lor \dots \lor X_{k}) = P (X_{1}) + P (X_{2}) + \dots + P (X_{k})

= \frac{1}{13} + \frac{1}{13}

\frac{1}{13} + \frac{1}{13} = \frac{2}{13}

= \frac{2}{13}