Answer : Option A

Explanation :

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Solution 1
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Total number of outcomes possible when a coin is tossed = 2 (∵ Head or Tail)
Hence, total number of outcomes possible when 3 coins are tossed, n(S) = 2 × 2 × 2 = 8
(∵ i.e., S = {TTT, TTH, THT, HTT, THH, HTH, HHT, HHH})
E = event of getting at most two Tails = {TTH, THT, HTT, THH, HTH, HHT, HHH}
Hence, n(E) = 7

$MF#%\text{P(E) = }\dfrac{\text{n(E)}}{\text{n(S)}} = \dfrac{7}{8}$MF#%

If n fair coins are tossed,

Total number of outcomes in the sample space = $MF#%2^n$MF#%

The probability of getting exactly r-number of heads when n coins are tossed = $MF#%\dfrac{n_{C_r}}{2^n}$MF#%