A bag contains 8 balls, of which 4 are white and the remaining are red...
Step I: Define Non-event
We are given that from a bag containing 4 red and 4 white balls, three balls are selected at random without replacement. We have to find the probability that at least one red ball is selected.
Now, following are the events in this case:
Event 1: One red ball is selected
Event 2: Two red balls are selected
Event 3: Three red balls are selected
However, there is only one non-event i.e. no red ball is selected. So, it will be easier to solve this question using the non-event approach.
So, we can write the probability event equation as:
P (At least one red ball is selected) = 1 – P (No red ball is selected)
Step II: Find n, the number of ways in which all outcomes can occur
Now, the total number of ways in which 3 balls can be selected from 8 balls is:
= 8C3 = 56
So, n = 8C3 = 56
Step III: Find x, the number of ways in which the Non-event can occur
Next, we are going to find the number of ways in which the non-event can occur.
As mentioned above, the non-event is that no red ball is selected among the three balls. This implies that the three selected balls are all white.
Now, the total number of white balls is 4.
So, we have to find the number of ways in which 3 white balls can be selected from 4 white balls.
Thus, x = 4C3 = 4
Step IV: Calculate probability for Non-event
P(No red ball is selected)
Step V: Probability (Event) = 1-Probability (Non-event)
P (At least one red ball is selected) = 1 – P (No red ball is selected)
Answer: Option (E)