Test question combination question

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    Combination Test
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SUMMARY

The problem involves determining the number of combinations for a student to answer 8 questions from a total of 12, with the requirement of selecting at least 4 from the first 5 questions. The solution involves calculating combinations using binomial coefficients: 5C4 + 5C5 for the first 5 questions, and then considering two scenarios: selecting 4 from the first 5 and 4 from the remaining 7 questions, or selecting 5 from the first 5 and 3 from the remaining 7. The final answer is obtained by summing the results of these two scenarios.

PREREQUISITES
  • Understanding of binomial coefficients (combinations)
  • Basic knowledge of combinatorial mathematics
  • Familiarity with the concept of constraints in combinatorial problems
  • Ability to perform calculations involving combinations
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  • Study the properties of binomial coefficients and their applications
  • Learn about combinatorial problem-solving techniques
  • Explore advanced topics in combinatorics, such as the Inclusion-Exclusion Principle
  • Practice solving similar combinatorial problems with varying constraints
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Students preparing for exams in combinatorial mathematics, educators teaching combinatorial concepts, and anyone interested in enhancing their problem-solving skills in mathematics.

Raerin
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There are 12 questions on an exam, and each student must answer 8 questions including at least 4 of the first 5 questions. How many different combinations of questions could a student choose to answer?

So I got the number of ways a student can choose to answer the first 5 questions which is 6 (5C4 + 5C5). I'm not sure what else to do.
 
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Raerin said:
There are 12 questions on an exam, and each student must answer 8 questions including at least 4 of the first 5 questions. How many different combinations of questions could a student choose to answer?

So I got the number of ways a student can choose to answer the first 5 questions which is 6 (5C4 + 5C5). I'm not sure what else to do.

The total number answered must be 8 and there are two ways of doing this with the other constraint.

1: 4 from the first 5 questions, 4 from the last 7
2: 5 from the first 5 questions, 3 from the last 7

Add up (1) and (2) and you'll get the answer.
 

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