Arithmetic Ability
Permutations and Combinations

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Q.

There are 2 brothers among a group of 20 persons. In how many ways can the group be arranged around a circle so that there is exactly one person between the two brothers?

View Answer

Correct choice: C

Explanation:

fix one person and the brothers B1 P B2 = 2 ways to do so. other 17 people= 17! Each person out of 18 can be fixed between the two=18, thus, 2 x 17! x 18=2 x 18!
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