CA Foundation · Quantitative Aptitude · Permutations and Combinations
From 6 teachers and 5 students, a panel of 4 is to be formed so that it contains at least one teacher and at least one student. How many such panels are possible?
The number of panels is 310. Total selections of 4 from 11 people are 330. Panels with only teachers number 15 and with only students number 5. Subtracting both unwanted groups from the total leaves 310 valid panels.
- A325Correct
- B330
- C310
- D315
Explanation
Total panels = 11C4 = 330. Remove all-teacher panels 6C4 = 15 and all-student panels 5C4 = 5. So 330 − 15 − 5 = 310. Option 325 subtracts only the 5 all-student panels, missing the all-teacher ones.
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