Question

Three unbiased coins are tossed together. Find the probability of getting all heads.

• A. $\frac{3}{8}$
• B. $\frac{1}{8}$
• C. $\frac{1}{4}$
• D. none of these

Answer 1

The correct option is B $\frac{1}{8}$

Three unbiased coins are tossed together.

Sample space, $S$

$=HHH,HHT,HTH,THH,TTH,THT,HTT,TTT$

Number of events, $n\left(S\right)=8$

For getting all heads, we will have the sample space,

$S_3=HHH$

Number of events, $n\left(S_3\right)=1$

Thus, probability of getting all heads

$P\left(S_3\right)=\frac{n\left(S_3\right)}{n\left(S\right)}$

$=\frac{1}{8}$