Question

Two men A & B draw alternate one ball each (with replacement) from a box containing 2 white and 4 red balls. If A is allowed to begin followed by B, the probability that B draws a white ball before A is :

• A. $\frac { 2 } { 45 }$
• B. $\frac { 2 } { 5 }$
• C. $\frac { 3 } { 5 }$
• D. $\frac { 1 } { 2 }$

Answer 1

Answer: (C)

$\frac { 3 } { 5 }$

Answer 2

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 = $\left( \frac { 4 } { 6 } \times \frac { 2 } { 6 } \right)$ + $\left( \frac { 4 } { 6 } \right) ^ { 3 }$ × $\left( \frac { 2 } { 6 } \right)$ + ...... [ G.P.] = $\frac { \frac { 8 } { 36 } } { 1 - \frac { 16 } { 36 } }$

= $\frac { 2 } { 5 }$