We know that,

Probability of occurrence of an event

 = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) 

By permutation and combination, total no. of ways to pick r objects from given n objects is ⁿC_r 

Now, total no. of ways to pick a ball from 20 balls is 20_c1 = 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 ¹⁶c₁ = 16 

Therefore, the probability of picking a white or red ball = \(\frac{16}{20}\) = \(\frac{4}{5}\) 

Conclusion: Probability of picking a white or red ball from 9 red, 7 white, and 4 black balls is \(\frac{4}{5}\)

We know that, 

Probability of occurrence of an event

 = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) 

By permutation and combination, total no. of ways to pick r objects from given n objects is ⁿC_r 

Now, total no. of ways to pick a ball from 20 balls is ²⁰c₁ = 20 

Our desired output is to pick a white ball. So, no. of ways to pick a white ball from 7 white balls(because the white ball can be picked from only white balls) is ⁷c₁ = 7 

Therefore, the probability of picking a white ball = \(\frac{7}{20}\)

Conclusion: Probability of picking a white ball from 9 red, 

7 white and 4 black balls is \(\frac{7}{20}\)

We know that 

Probability of occurrence of an event

= \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) 

By permutation and combination, total no. of ways to pick r objects from given n objects is ⁿC_r 

Now, total no. of ways to pick a ball from 20 balls is ²⁰c₁ = 20 

Our desired output is to pick a red ball. So, no. of ways to pick a red ball from 9 red balls (because the red ball can be picked from only red balls) is ⁹c₁ = 9

Therefore, the probability of picking a red ball = \(\frac{9}{20}\)

Conclusion: Probability of picking a red ball from 9 red, 

7 white and 4 black balls is  \(\frac{9}{20}\)

We know that, 

Probability of occurrence of an event 

 = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) 

By permutation and combination, total no. of ways to pick r objects from given n objects is ⁿC_r 

Now, total no. of ways to pick a ball from 20 balls is ²⁰c₁ = 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 ¹⁶c₁ = 16 

Therefore, the probability of picking a white or black ball = \(\frac{11}{20}\) 

Conclusion: Probability of picking a white or black ball from 9 red, 7 white, and 4 black balls is  \(\frac{11}{20}\)