An urn contains 9 red, 7 white, and 4 black balls. A ball is drawn at random. Find the probability that the ball is drawn is
white or black
We know that,
Probability of occurrence of an event
$=\frac{\text { Total no. of Desired outcomes }}{\text { Total no.of outcomes }}$
By permutation and combination, total no. of ways to pick r objects from given $n$ objects is ${ }^{\mathrm{n}} \mathrm{C}_{\mathrm{r}}$
Now, total no. of ways to pick a ball from 20 balls is ${ }^{20} \mathrm{C} 1=20$
Our desired output is to pick a white or red ball. So, no. of ways to pick a white or red ball from 16 balls(because there are a total of 16 balls which are either red or white) is ${ }^{16} \mathrm{C}_{1}=16$
Therefore, the probability of picking a white or black ball $=\frac{11}{20}$
$=\frac{11}{20}$
Conclusion: Probability of picking a white or black ball from 9 red, 7 white, and 4 black balls is $\frac{11}{20}$
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.