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In an examination a question paper …

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In an examination a question paper consist of 12 questions divided into parts A and B. Part A contains 5 questions and part B contains 7 questions respectively. A candidate is required to attempt 8 questions selecting at least 3 from each part. In how many ways can a candidate select the questions?
  • 2 answers

Gaurav Seth 6 years, 10 months ago

Given, total number of questions = 12

Part 1 contains 5 questions and part 2 contain 7 questions.

A student has to select 8 questions all in which there is at least 3 questions from each part. 

Now different possibilities can occur.

   Part1 (5 questions)            Part2 (7 questions)

           3                                    5

           4                                    4

           5                                    3

Now total number of ways is

    ( 5C3 * 7C5 ) + ( 5C4 * 7C4 ) + ( 5C5* 7C3 )

= ( 5C2 * 7C2 ) + ( 5C1 * 7C3 ) + ( 5C0* 7C3 )

= {(5*4*7*6)/(2*2)} + {(5*7*6*5)/(3*2)} + {(7*6*5)/(3*2)}

= 210 + 175 + 35

= 420 

So, the total number of ways a student can select the questions is 420

Prashant Singh 6 years, 10 months ago

420
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