Probability - Arithmetic Aptitude Questions and Answers

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A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?

$\frac { 10 } { 2 1}$

$\frac { 11 } { 2 1}$

$\frac { 2} { 7 }$

$\frac { 5} { 7 }$

Answer : Option A

Explanation :

Total number of balls = (2 + 3 + 2) = 7.

Let S be the sample space.

Then,= Number of ways of drawing 2 balls out of 7

= 7c₂

_{= $\frac { (7*6) } { (2 *1)}$}

_{= 21}

Let E = Event of drawing 2 balls, none of which is blue.

n(E)Number of ways of drawing 2 balls out of (2 + 3) balls

=5C₂

= $\frac { (5*4) } { (2 *1)}$

=10

P (E) = $\frac { n (E)} {n(s)}$ = $\frac { 10 } { 2 1}$

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