An ordinary die is tossed. What is the probability of getting a 3 or a 4?

해법

A n or d ina ry d i e i s t osse d . Wha t i s t h e p ro babi l i t y o f g e tt in g a 3 or a 4 ?

\frac{1}{3}

소수

0.33333 \dots

솔루션 단계

Find the probability of getting a 3:

\frac{1}{6}

Find the probability of a 4:

\frac{1}{6}

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}{6} + \frac{1}{6}

\frac{1}{6} + \frac{1}{6} = \frac{1}{3}

= \frac{1}{3}