Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrMedium2 minQB

MathematicsMediumsingle choice

Passage / Comprehension

Let S be the set of the first 18 positive integers.

The number of ways of selecting three numbers from S such that they form an A.P. is

Answer:

Solution:

Number of ways of selecting 2 even integers $= 9 C_{2}$

Number of ways of selecting 2 odd integers $= 9 C_{2}$

∴ Total number of ways of selecting two integers so that their sum is even $= 2 \times 9 C_{2} = 72$

Stream:JEESubject:MathematicsTopic:Permutation & CombinationSubtopic:nPr & nCr

⏱ 2mℹ️ Source: QB

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