
‣ A coin is tossed three times.

‣ The probability of getting,
1) Exactly 3 tails 
2) At most 2 heads
3) At least 2 tails 
4) Exactly 2 heads 
5) Exactly 3 heads



★ When three coins are tossed,
then the sample space = {HHH, HHT, THH, TTH, HTH, HTT, THT, TTT}
[here H denotes head and T denotes tail]
⇒Total number of outcomes ![\tt [ \: n(s) \: ]](https://tex.z-dn.net/?f=%20%5Ctt%20%5B%20%5C%3A%20n%28s%29%20%5C%3A%20%5D%20) = 8
 = 8
<u>1) Exactly 3 tails </u>
Here 
• Favourable outcomes = {HHH} = 1 
• Total outcomes = 8 

<u>2) At most 2 heads</u>
[It means there can be two or one or no heads]
Here 
• Favourable outcomes = {HHT, THH, HTH, TTH, HTT, THT, TTT} = 7
• Total outcomes = 8 

<u>3) At least 2 tails </u>
[It means there can be two or more tails]
Here 
• Favourable outcomes = {TTH, TTT, HTT, THT} = 4
• Total outcomes = 8 


<u>4) Exactly 2 heads </u>
Here 
• Favourable outcomes = {HTH, THH, HHT } = 3
• Total outcomes = 8 

<u>5) Exactly 3 heads</u>
Here 
• Favourable outcomes = {HHH} = 1
• Total outcomes = 8 

