You are dealt one card from a 52-card deck. Find the probability that you are dealt a three or a red card.

Решение

Y o u a re d e a lt o n e c a r d f ro m a ​ 52 - c a r d d ec k . F in d t h e p ro babi l i t y t ha t yo u a re d e a lt a t h ree or a re d c a r d .

\frac{7}{13}

десятичными цифрами

0.53846 \dots

Шаги решения

Find the probability of you are dealt a 3:

\frac{1}{13}

Find the probability of a red card:

\frac{1}{2}

Find the probability of you are dealt a 3 and a red card:

\frac{1}{26}

Use the Inclusion-Exclusion formula

P (X \lor Y) = P (X) + P (Y) - P (X \land Y)

= \frac{1}{13} + \frac{1}{2} - \frac{1}{26}

\frac{1}{13} + \frac{1}{2} - \frac{1}{26} = \frac{7}{13}

= \frac{7}{13}