In a group of 16 students, how many different ways can you select a team of 4 students to participate in a quiz if at least 2 of them must be from a specific grade?
205
846
302
105
To solve this problem, we'll consider two cases: when exactly 2 students are chosen from the specific grade and when 3 or more students are chosen from the specific grade.
Case 1: Exactly 2 students from the specific grade are chosen.
In this case, we need to select the remaining 2 students from the remaining 16-2=14 students (excluding the 2 from the specific grade).
Number of ways to select 2 students from 14=14 C2
Case 2: 3 or more students from the specific grade are chosen.
In this case, we can choose 3 or 4 students from the specific grade. Let's consider each sub-case:
Sub-case 1: 3 students from the specific grade are chosen.
We need to select the remaining 1 student from the remaining 16-3=13 students.
Number of ways to select 1 student from 13=13 C1
Sub-case 2: All 4 students from the specific grade are chosen.
There is only 1 way to select all 4 students from the specific grade.
To calculate the total number of ways to form the team, we need to sum up the possibilities from both cases and all sub-cases:
Total number of ways = Number of ways in Case 1+ Number of ways in Sub-case 1+ Number of ways in Sub-case 2
Total number of ways =14 C 2+13 C 1+1
Now, let's calculate the value:
Total number of ways =91+13+1=105
Therefore, there are 105 different ways to select a team of 4 students to participate in the quiz, where at least 2 of them must be from a specific grade.
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