Three coins are tossed once. Find the probability of getting atmost two tails.
Three coins are tossed once. Find the probability of getting atmost two tails.
When three coins are tossed once, the sample space is given by $S =\{ HHH , HHT , HTH , THH , HTT , THT , TTH , TTT \}$
$\therefore$ Accordingly, $n ( S )=8$
It is known that the probability of an event $A$ is given by
$P ( A )=\frac{\text { Number of outcomes favourable to } A }{\text { Total number of possible outcomes }}=\frac{n( A )}{n( S )}$
Let $J$ be the event of the occurrence of at most $2$ tails.
Accordingly, $J=\{H H H,\, H H T , \,H T H , \,T H H , \,H T T , \,T H T , \, T T H \} ~$
$\therefore P(J)=\frac{n(J)}{n(S)}=\frac{7}{8}$
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- [IIT 1998]
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