Saved Bookmarks
| 1. |
A box contains 8 white balls and 9 red balls. Two balls are taken at random from the box. Find the probability that both of them are red if (i) The two balls are taken together. (ii) The balls are taken one after the other without replacement. (iii) The balls are taken one after the other with replacement. |
|
Answer» (i) Two balls are selected from 17 balls in 17C2w ways Ways of choosing 2 Red balls from 9 red is 9C2 ways. ∴ (P both red) = \(\frac{^9C_2}{^{17}C_2} = \frac{9}{34}\) (ii) Without replacement, probability of 1st red ball = \(\frac{9}{17}\) And also probability of 2nd red ball is = \(\frac{8}{16}\) (iii) With replacement Probability of 1st red ball = \(\frac{9}{17}\) And also probability of 2nd red ball is = \(\frac{9}{17}\) ∴ P(both red) = \(\frac{9}{17}\) x \(\frac{9}{17}\)= \(\frac{81}{289}\) |
|