What is the probability of throwing a 3 or a 5 in one roll of an ordinary die?

解

Wha t i s t h e p ro babi l i t y o f t h ro w in g a 3 or a 5 in o n e ro ll o f an or d ina ry d i e ?

\frac{1}{3}

十進法表記

0.33333 \dots

解答ステップ

Find the probability of throwing a 3:

\frac{1}{6}

Find the probability of a 5 in 1 roll of an ordinary die:

\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}