Question

A and B toss a coin alternatively, the first to show a head

being the winner. If A starts the game, the chance of his

winning is-

• A. 5/8
• B. ½
• C. 1/3
• D. 2/3

Answer 1

Answer: (D)

2/3

Answer 2

P(1) = P(2) = $\frac { 1 } { 2 }$

Probability of wining of A = P(1) + P($\overline { \mathrm { A } }$) P() P (1) +

P( $\overline { \mathrm { A } }$ ) P() P( $\overline { \mathrm { A } }$ ) P( $\overline { \mathrm { B } }$ ) P(1) + ……….. 

= $\frac { \mathrm { P } ( \mathrm { A } ) } { 1 - \mathrm { P } ( \overline { \mathrm { A } } ) \mathrm { P } ( \overline { \mathrm { B } } ) }$ = $\frac { 1 } { 2 }$