Three unbiased coins are tossed simultaneously. Find the probability of getting exactly ^@2^@ heads.
Answer:
^@ \dfrac { 3 } { 8 } ^@
- When ^@3 ^@ coins are tossed simultaneously, all the possible outcomes are
^@
HHH, HHT, HTH, THH, HTT, THT, TTH,^@ and ^@TTT.
^@
So, total number of possible outcomes = ^@ 8 ^@. - Let ^@ E ^@ be the event of getting exactly ^@ 2 ^@ heads.
The favourable outcomes are ^@ HHT, HTH, ^@ and ^@ THH. ^@
Number of favouable outcomes = ^@ 3 ^@ @^ \begin{aligned} \therefore \space P(\text{ getting exactly 2 heads }) = P(E) = \dfrac { \text { Number of favourable outcomes } } { \text { Total number of outcomes } } = \dfrac { 3 } { 8 }. \end{aligned} @^ Thus, the probability of getting exactly ^@ 2 ^@ heads = ^@ \dfrac { 3 } { 8 } ^@