To fill 12 vacancies, there are 25 candidates of which five are from the scheduled caste. If 3 of the vacancies are reserved for scheduled caste candidates while the rest are open to all, then the number of ways in which the selection can be made is:
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When selecting candidates with restrictions (e.g., reserved categories), first handle the restricted choices, then handle the remaining free choices.
Step 1: There are 12 vacancies to be filled, and 3 of these vacancies are reserved for candidates from the scheduled caste.
- The number of ways to select 3 candidates from the 5 scheduled caste candidates is \( 5C3 \).
- After selecting the 3 scheduled caste candidates, 9 vacancies remain, and they can be filled by any of the remaining 22 candidates. The number of ways to select 9 candidates from the 22 is \( 22C9 \). Step 2: Therefore, the total number of ways to fill the vacancies is:
\[
5C3 \times 22C9.
\]