In Grand Oberoi hotel, 1160 guests are present currently. The hotel provides the following extra facilities: Gym, Swimming, Fun park, Food. During a regular survey the management team of Oberoi noticed something quite extraordinary about the extra facilities provided by them. They noticed that for every person who uses ‘F’ no. of facilities, there are exactly 3 persons who uses at least (F-1) no. of facilities, F = 2, 3, 4. They also found that the no. of persons who used no extra facilities is twice the no of person that used all the 4 facilities. Help the management team to find out how many persons used exactly 3 facilities.
A. 20
B. 40
C. 60
D. 80
E. 100
Basically, question is saying that if n is number of persons using 3 facilities, then \(\frac{n}{3}\) is the number of people who use 4 facilities.
Let number of people using 3 facilities,\(F_3 = n\)
Then Number of people using 2 facilities,\(F_2 = 3n\)
Number of people using 1 facility,\(F_1 = 9n\)
Number of people using 4 facilities,\(F_4 = \frac{n}{3}\)
Number of people using 0 facilities,\(F_0 = 2\frac{n}{3}\)
Hence,
\(\frac{n}{3} + n + 3n + 9n + 2\frac{n}{3} = 1160\)
n + 3n + 9n + 27n + 2n = 1160*3
42n = 1160*3
\(n = \frac{580}{7}\) ~80
IMO Answer D.
PS: The number here should be a multiple of 3, accordingly only C satisfies this condition. Also, on verifying none of the options satisfy all conditions laid by the question. Don't what am i missing?