If two coins are tossed once, what is the probability of getting: (i) both heads. (ii) at least one head.

Solution:

We know that, when two coins are tossed together possible number of outcomes = {HH, TH, HT, TT}

So, \[n\left( S \right)\text{ }=\text{ }4\]

\[\left( i \right)\]E = event of getting both heads = {HH}

\[n\left( E \right)\text{ }=\text{ }1\]

Hence, probability of getting both heads \[=~n\left( E \right)/\text{ }n\left( S \right)\text{ }=\text{ }{\scriptscriptstyle 1\!/\!{ }_4}\]

\[\left( ii \right)\]E = event of getting at least one head = {HH, TH, HT}

\[n\left( E \right)\text{ }=\text{ }3\]

Hence, probability of getting at least one head \[=~n\left( E \right)/\text{ }n\left( S \right)\text{ }=\text{ }{\scriptscriptstyle 3\!/\!{ }_4}\]