Answer:
(a) 
(b) 
(c) 
Step-by-step explanation:
Given,
The total number of balls = 100,
Red balls = r
So, the remaining balls = 100 - r,
(a) ∵ The probability that first ball drawn will be red


(b) Also, the probability of a ball other than red ball = 

So, the probability of getting red ball in second thrawn( one is red second is red or one is not red second is red ),

![=\frac{r}{99}[\frac{r-1}{100}+\frac{100-r}{100}]](https://tex.z-dn.net/?f=%3D%5Cfrac%7Br%7D%7B99%7D%5B%5Cfrac%7Br-1%7D%7B100%7D%2B%5Cfrac%7B100-r%7D%7B100%7D%5D)
![=\frac{r}{99}[\frac{r-1+100-r}{100}]](https://tex.z-dn.net/?f=%3D%5Cfrac%7Br%7D%7B99%7D%5B%5Cfrac%7Br-1%2B100-r%7D%7B100%7D%5D)
![=\frac{r}{99}[\frac{99}{100}]](https://tex.z-dn.net/?f=%3D%5Cfrac%7Br%7D%7B99%7D%5B%5Cfrac%7B99%7D%7B100%7D%5D)

Now, the the probability of getting red ball in third thrawn,


......so on,...
This pattern will be followed in every trials,
Hence, the probability that the 50th ball drawn will be red = 
(c) Similarly, the probability that the last ball drawn will be red = 