number of ways

The number of ways in which we can select four numbers from 1 to 30 so as to exclude every selection of four consecutive numbers is????

6 Answers

³⁰C₄ - 27

yup good solution :)

but answer is 27378

His number is 27405-27 = 27378 :P

@ abhirup ..........can u explain your answer...............

no of ways of selecting 4 numbers=30C4

number of ways of selecting 4 consecutive nos is : 27 (why? this is simple.. just think a bit)

So the diff gives the answer

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∑ ∑ ∑ ∑ ∑ ∮ ∮ ∮ ∮ ∮ ∏ ∏ ∏ ∏ ∏ ∐ ∐ ∐ ∐ ∐

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