From a group of 8 volunteers, including andrew and karen, 4 people are to be selected at random to organize a charity event. what is the probability that andrew will be among the 4 volunteers selected and karen will not? a. 3/7b. 5/12c. 27/70d. 2/7e. 9/35

D. 2/7

Step-by-step explanation:

The probability is calculate as a division between the number of ways in which Andrew will be selected and karen will not and the total ways in which they can select 4 people from a group of 8 volunteers.

The number of ways in which they can select 4 people from a group of 8 volunteers can be calculated using:

Where nCk give as the number of ways in which we can form groups of k elements from a group of n elements.

So, if we replace n by 8 and k by 4, we get:

Then, there are 70 ways to select 4 people from a group of 8 volunteers.

At the same way, the number of ways in which Andrew will be selected and karen will not can be calculate replacing n by 6 and k by 3 in the same equation as:

We replace n by 6 because from the 8 volunteers, Andrew is going to be selected and Karen will not, so, the people that affect the result are just the 6 remaining volunteers. Also, k is equal to 3 because Andrew is already selected and we just need to select 3 more people.

Finally, the probability is:

final answer is : )

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