Question
A bag contains 6 white and 4 black balls. Two balls are drawn at random. Find the probability that they are of same colour.
Answer: Option D
Number of ways two balls can be drawn from 10 balls (6 white +4 blacks)
$$ = {}^{10}{C_2} = \frac{{10 \times 9}}{{2 \times 1}} = 45$$
n(E) = Number of ways of drawing 2 balls from 6 white balls or 2 balls from 4 black balls
$$\eqalign{
& = {}^6{C_2} + {}^4{C_2} = 21 \cr
& {\text{P}}\left( {\text{E}} \right) = \frac{{21}}{{45}} = \frac{7}{{15}} \cr} $$
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Number of ways two balls can be drawn from 10 balls (6 white +4 blacks)
$$ = {}^{10}{C_2} = \frac{{10 \times 9}}{{2 \times 1}} = 45$$
n(E) = Number of ways of drawing 2 balls from 6 white balls or 2 balls from 4 black balls
$$\eqalign{
& = {}^6{C_2} + {}^4{C_2} = 21 \cr
& {\text{P}}\left( {\text{E}} \right) = \frac{{21}}{{45}} = \frac{7}{{15}} \cr} $$
Was this answer helpful ?
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