To solve the given problem, we need to address each part separately:
a. To find the number of different ways to appoint the officers, we need to consider the permutations of 16 candidates taken 4 at a time (since the order matters for positions).
b. To find the number of different ways to appoint the committee, we need to consider the combinations of 16 candidates taken 4 at a time (since the order does not matter for committee members).
c. To find the probability of randomly selecting the committee members and getting the four youngest candidates, we need to calculate the number of favorable outcomes (which is 1, since there is only one way to choose the four youngest) divided by the total number of ways to choose 4 candidates out of 16.
To determine the number of different ways to appoint the officers (president, vice-president, secretary, and treasurer) from 16 candidates, we use the permutation formula:
\[
P(n, r) = \frac{n!}{(n - r)!}
\]
where \( n = 16 \) and \( r = 4 \). Thus, the calculation is:
\[
P(16, 4) = \frac{16!}{(16 - 4)!} = 16 \times 15 \times 14 \times 13 = 43680
\]
To find the number of different ways to appoint a planning committee of 4 members from the same 16 candidates, we use the combination formula:
\[
C(n, r) = \frac{n!}{r!(n - r)!}
\]
where \( n = 16 \) and \( r = 4 \). Thus, the calculation is:
\[
C(16, 4) = \frac{16!}{4! \times (16 - 4)!} = \frac{16 \times 15 \times 14 \times 13}{4 \times 3 \times 2 \times 1} = 1820
\]
To find the probability of randomly selecting the four youngest candidates for the committee, we calculate:
\[
P(\text{four youngest}) = \frac{\text{favorable outcomes}}{\text{total outcomes}} = \frac{1}{1820}
\]
This results in:
\[
P(\text{four youngest}) \approx 0.0005495
\]
- There are \( \boxed{43680} \) different ways to appoint the officers.
- There are \( \boxed{1820} \) different ways to appoint the committee.
- The probability of getting the four youngest candidates is \( \boxed{0.0005495} \).