Difference between revisions of "2024 AMC 10A Problems/Problem 9"

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== Video Solution 1 by Power Solve ==
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https://youtu.be/j-37jvqzhrg?si=IBSPzNSvdIodGvZ7&t=1145
  
 
==See also==
 
==See also==
 
{{AMC10 box|year=2024|ab=A|num-b=8|num-a=10}}
 
{{AMC10 box|year=2024|ab=A|num-b=8|num-a=10}}
 
{{MAA Notice}}
 
{{MAA Notice}}

Revision as of 18:57, 8 November 2024

Problem

In how many ways can 6 juniors and 6 seniors form 3 disjoint teams of 4 people so that each team has 2 juniors and 2 seniors?

Solution 1

The number of ways in which we can choose the juniors for the team are ${6\choose2}{4\choose2}{2\choose2}=90$. Similarly, the number of ways to choose the seniors are the same, so the total is $90\cdot90=8100$. But we must divide the number of permutations of three teams, which is $3!$. Thus the answer is $\frac{8100}{3!}=\frac{8100}{6}=\boxed{1350}$.

~eevee9406

Solution 2

Let the three teams be team A, team B, and team C. There are $\binom{6}{2} = 15$ ways to choose the two seniors for team A. Then, out of the remaining four, there are $\binom{4}{2} = 6$ ways to choose two seniors for team B. Then, the remaining two seniors must be on team C. Thus, there are $15 \cdot 6 = 90$ ways to choose seniors for all the teams.

Similarly, there are $90$ ways to choose juniors for the three teams, so there are $90 \cdot 90 = 8100$ ways in total. However, since the teams are symmetric, we must divide by $3! = 6$, so the final answer is $\frac{8100}{6} = \boxed{\textbf{(B)} 1350}$

~andliu766

Video Solution 1 by Power Solve

https://youtu.be/j-37jvqzhrg?si=IBSPzNSvdIodGvZ7&t=1145

See also

2024 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 8
Followed by
Problem 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AMC 10 Problems and Solutions

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