If you draw one card from a standard deck, what is the probability of drawing a spade or a red card?

解

I f yo u d r a w o n e c a r d f ro m a s t an d a r d d ec k, w ha t i s t h e p ro babi l i t y o f d r a w in g a s p a d e or a re d c a r d ?

\frac{3}{4}

十進法表記

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解答ステップ

Find the probability of drawing a spade:

\frac{1}{4}

Find the probability of a red card:

\frac{1}{2}

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}{4} + \frac{1}{2}

\frac{1}{4} + \frac{1}{2} = \frac{3}{4}

= \frac{3}{4}