OA is D 2*18!

here is the explanation.

Let us assume that 2 brother and one person in between them as single entity. So total no of objects to arrange now are = 20 â€“ 2 â€“1 + 1

(considering those 3 as one) = 18

Circular combination of arranging 18 object is = (18 â€“1)! = 17!

Now each of the other 18 person can come in between those 2 brothers, so total no of ways = 18 * 17!

Now 2 brother can switch there seat in 2 ways. Hence total no of ways = 2*18*17!= 2*18!

cool_jonny009 wrote:

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?

(a) 2 * 19!

(b) 18! * 18

(c) 19! * 18

(d) 2 * 18!

(e) 17*18!