Question

In tossing a fair coin twice, find the probability of getting two heads

Answer 1

When a fair coin is tossed twice, $S=\{HH,TT,HT,TH\}\therefore n\left(S\right)=4$
Let $A$ be the event of getting two heads
$A=\left\{HH\right\}\therefore n\left(A\right)=1$
$\therefore P\left(A\right)=\frac{n\left(A\right)}{n\left(S\right)}=\frac{1}{4}$