One card is selected at random from a deck of cards. Determine the probability of selecting a card that is less than 4 or a spade.

Решение

O n e c a r d i s se l ec t e d a t r an d o m f ro m a d ec k o f c a r d s . De t er min e t h e p ro babi l i t y o f se l ec t in g a c a r d t ha t i s l ess t han 4 or a s p a d e .

\frac{19}{52}

десятичными цифрами

0.36538 \dots

Шаги решения

Find the probability of selecting a card that is less than 4:

\frac{2}{13}

Find the probability of a spade:

\frac{1}{4}

Find the probability of selecting a card that is less than 4 and a spade:

\frac{1}{26}

Use the Inclusion-Exclusion formula

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

= \frac{2}{13} + \frac{1}{4} - \frac{1}{26}

\frac{2}{13} + \frac{1}{4} - \frac{1}{26} = \frac{19}{52}

= \frac{19}{52}