Question

A coin is tossed three times in succession. If E is the event that there are at least two heads and F is the event in which first throw is a head, then $P \left( \frac { E } { F } \right) =$

• A. $\frac { 3 } { 4 }$
• B. $\frac { 3 } { 8 }$
• C. $\frac { 1 } { 2 }$
• D. $\frac { 1 } { 8 }$

Answer 1

Answer: (A)

$\frac { 3 } { 4 }$

Answer 2

$S = \{ H H H , H H T , H T H , T H H , H T T , T H T , T T H , T T T \}$

$n ( E \cap F ) = 3$

∴ $P \left( \frac { E } { F } \right) = \frac { P ( E \cap F ) } { P ( F ) } = \frac { 3 / 8 } { 4 / 8 } = \frac { 3 } { 4 }$.