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A team of 11 students is to be formed from a group of 18 students - HSC - SSCE Mathematics Extension 1 - Question 8 - 2016 - Paper 1

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A team of 11 students is to be formed from a group of 18 students. Among the 18 students are 3 students who are left-handed. What is the number of possible teams co... show full transcript

Worked Solution & Example Answer:A team of 11 students is to be formed from a group of 18 students - HSC - SSCE Mathematics Extension 1 - Question 8 - 2016 - Paper 1

Step 1

Calculate the total number of ways to choose 11 students from 18 students

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Answer

To find the total number of ways to form a team of 11 students from 18, we use the combination formula:

C(n,k)=n!k!(nk)!C(n, k) = \frac{n!}{k!(n-k)!}

Here, (n = 18) and (k = 11):

C(18,11)=18!11!(1811)!=18!11!7!C(18, 11) = \frac{18!}{11! \cdot (18 - 11)!} = \frac{18!}{11! \cdot 7!}

Calculating this gives:

C(18,11)=31824C(18, 11) = 31824

Step 2

Calculate the number of ways to choose 11 students with no left-handed students

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Answer

The number of right-handed students is 18 - 3 = 15. To find the number of teams consisting of only right-handed students, we again use the combination formula:

C(15,11)=15!11!(1511)!=15!11!4!C(15, 11) = \frac{15!}{11! \cdot (15 - 11)!} = \frac{15!}{11! \cdot 4!}

Calculating this gives:

C(15,11)=1365C(15, 11) = 1365

Step 3

Subtract to find the number of teams with at least 1 left-handed student

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Answer

To find the number of teams containing at least 1 left-handed student, we subtract the number of teams with no left-handed students from the total number of teams:

Number of teams with at least 1 left-handed student = Total ways - No left-handed = 31824 - 1365 = 30459.

Thus, the final answer is 30,459.

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