Math Problem Statement

There are ‘N’ total students in a class of which ‘m’ are female and the rest are male. If 5

students are picked at random for the “dress code enforcement committee” on

campus, calculate the probability that

a. The committee will only have female students.

b. The committee will only have male students.

Solution

Let's solve the problem by first understanding the setup and then applying the principles of combinatorics and probability.

Given:

  • Total number of students in the class: NN
  • Number of female students: mm
  • Number of male students: NmN - m (since the rest are male)
  • Number of students selected for the committee: 5

Part (a): Probability that the committee will only have female students

Step 1: Determine the total number of ways to select 5 students from NN students

The number of ways to choose 5 students out of NN is given by the combination formula:

Total combinations=(N5)=N!5!(N5)!\text{Total combinations} = \binom{N}{5} = \frac{N!}{5!(N-5)!}

Step 2: Determine the number of ways to select 5 female students from mm female students

The number of ways to choose 5 female students out of mm is given by:

Female combinations=(m5)=m!5!(m5)!\text{Female combinations} = \binom{m}{5} = \frac{m!}{5!(m-5)!}

Step 3: Calculate the probability

The probability that all 5 students selected are female is:

P(only females)=Female combinationsTotal combinations=(m5)(N5)=m!5!(m5)!N!5!(N5)!=m(m1)(m2)(m3)(m4)N(N1)(N2)(N3)(N4)P(\text{only females}) = \frac{\text{Female combinations}}{\text{Total combinations}} = \frac{\binom{m}{5}}{\binom{N}{5}} = \frac{\frac{m!}{5!(m-5)!}}{\frac{N!}{5!(N-5)!}} = \frac{m(m-1)(m-2)(m-3)(m-4)}{N(N-1)(N-2)(N-3)(N-4)}

Part (b): Probability that the committee will only have male students

Step 1: Determine the number of ways to select 5 male students from NmN - m male students

The number of ways to choose 5 male students out of NmN - m is given by:

Male combinations=(Nm5)=(Nm)!5!(Nm5)!\text{Male combinations} = \binom{N-m}{5} = \frac{(N-m)!}{5!(N-m-5)!}

Step 2: Calculate the probability

The probability that all 5 students selected are male is:

P(only males)=Male combinationsTotal combinations=(Nm5)(N5)=(Nm)!5!(Nm5)!N!5!(N5)!=(Nm)(Nm1)(Nm2)(Nm3)(Nm4)N(N1)(N2)(N3)(N4)P(\text{only males}) = \frac{\text{Male combinations}}{\text{Total combinations}} = \frac{\binom{N-m}{5}}{\binom{N}{5}} = \frac{\frac{(N-m)!}{5!(N-m-5)!}}{\frac{N!}{5!(N-5)!}} = \frac{(N-m)(N-m-1)(N-m-2)(N-m-3)(N-m-4)}{N(N-1)(N-2)(N-3)(N-4)}

Final Answers:

  • (a) The probability that the committee will only have female students is:

P(only females)=(m5)(N5)\boxed{P(\text{only females}) = \frac{\binom{m}{5}}{\binom{N}{5}}}

  • (b) The probability that the committee will only have male students is:

P(only males)=(Nm5)(N5)\boxed{P(\text{only males}) = \frac{\binom{N-m}{5}}{\binom{N}{5}}}

Do you want more details or have any questions?

Here are some related questions:

  1. How does the probability change if the committee size is increased to 6?
  2. What is the probability that the committee will have exactly 3 female students?
  3. How would the probability change if mm and NmN-m are very close in value?
  4. What is the probability that the committee will have at least one female student?
  5. How would you calculate the expected number of female students in the committee?

Tip: When dealing with probabilities in combinatorial problems, always remember to clearly identify the total possible outcomes and the favorable outcomes before calculating the probability.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Combinatorics
Probability

Formulas

Combinations formula

Theorems

-

Suitable Grade Level

High School