Study the following information and answer the questions that follow ::
In a big hotel, there are 1,000 rooms. In the hotel only even numbers are used for room numbers i.e the room numbers 2,4,6,...1998,2000. All the rooms have one resident each. One fine morning, the warden calls all the residents and tells them to go back to their rooms as well as multiples of their room numbers. When a guy visit a room and finds the door open, he closes it and if the door is closed, he opens it. All 1,000 guys do this operation. All the doors were open initially.
Answer: C If a room has an odd number of visitors, it will be closed. Any room number that is twice a perfect square will have an odd number of visitors. The room with the largest such number (twice a perfect square) will be the last room to have an odd number of visitors. Note that the 38th room with an open door will be 38th room whose number is not twice a perfect square, which happens to be 88. A, 2000 is in open state initially. And if all the occupants have to do the job then it will remain open as well. Now as occupant of 2000 will not have to do that. And action done by all the occupants from 2 to 1000 will bring that in closed state. Number of room closed upto 1000 = 22 Since there are 22 twice a perfect square numbers. Number of remaining room = 500 Number of twice a perfect number between 1000 and 2000 = 9. All rooms with the twice a perfect square between 1000 and 2000 will be open. Number of room closed = 22+500-9 = 513.
Answer: B If a room has an odd number of visitors, it will be closed.
Any room number that is twice a perfect square will have an odd number
of visitors. The room with the largest such number (twice a perfect
square) will be the last room to have an odd number of visitors.
Note that the 38th room with an open door will be 38th room whose number is not twice a perfect square, which happens to be 88.
A, 2000 is in open state initially. And if all the occupants have to do
the job then it will remain open as well. Now as occupant of 2000 will
not have to do that. And action done by all the occupants from 2 to 1000
will bring that in closed state.
Number of room closed upto 1000 = 22
Since there are 22 twice a perfect square numbers.
Number of remaining room = 500
Number of twice a perfect number between 1000 and 2000 = 9.
All rooms with the twice a perfect square between 1000 and 2000 will be open.
Number of room closed = 22+500-9 = 513.
Q. No. 3:
If only 500 guys i.e residents of room number 2 to 1000 do the task, then the last room that is closed is room number.
Answer: A If a room has an odd number of visitors, it will be closed.
Any room number that is twice a perfect square will have an odd number
of visitors. The room with the largest such number (twice a perfect
square) will be the last room to have an odd number of visitors.
Note that the 38th room with an open door will be 38th room whose number is not twice a perfect square, which happens to be 88.
A, 2000 is in open state initially. And if all the occupants have to do
the job then it will remain open as well. Now as occupant of 2000 will
not have to do that. And action done by all the occupants from 2 to 1000
will bring that in closed state.
Number of room closed upto 1000 = 22
Since there are 22 twice a perfect square numbers.
Number of remaining room = 500
Number of twice a perfect number between 1000 and 2000 = 9.
All rooms with the twice a perfect square between 1000 and 2000 will be open.
Number of room closed = 22+500-9 = 513.
Q. No. 4:
In the case of question number 3, how many rooms will be closed in all ?
Answer: A If a room has an odd number of visitors, it will be closed.
Any room number that is twice a perfect square will have an odd number
of visitors. The room with the largest such number (twice a perfect
square) will be the last room to have an odd number of visitors.
Note that the 38th room with an open door will be 38th room whose number is not twice a perfect square, which happens to be 88.
A, 2000 is in open state initially. And if all the occupants have to do
the job then it will remain open as well. Now as occupant of 2000 will
not have to do that. And action done by all the occupants from 2 to 1000
will bring that in closed state.
Number of room closed upto 1000 = 22
Since there are 22 twice a perfect square numbers.
Number of remaining room = 500
Number of twice a perfect number between 1000 and 2000 = 9.
All rooms with the twice a perfect square between 1000 and 2000 will be open.
Number of room closed = 22+500-9 = 513.
Study the following questions and answer the questions that follow ::
P,Q,R and S are four siblings of different genders- two males (M) and two females (F), it is known that Q is younger to P, S is younger to R and S is a female.
Q. No. 1:
The gender of P can be determined, if the siblings in the decreasing order of their ages are :
Answer: A Note that the sequence (in decreasing order of ages of siblings) can be PQRS, RPQS, PRQS, PRSQ, RPSQ and in terms of gender M,F(male, female): MMFF, MFMF, MFFM, FFMM, FMFM and FMMF. These can be arranged as possibilities. MMFF -PQRS, RPQS, PRQS, PRSQ, RPSQ MFMF -PQRS, RPQS, PRQS, RSPQ MFFM -PRSQ, RPSQ, RSPQ FFMM -RSPQ FMFM - RPSQ, PRSQ FMMF - PQRS, RPQS, PRQS
Q. No. 2:
The gender of Q cannot be determined, if the siblings in the decreasing order of their ages are :
Answer: A Note that the sequence (in decreasing order of ages of siblings)
can be PQRS, RPQS, PRQS, PRSQ, RPSQ and in terms of gender M,F(male, female): MMFF, MFMF, MFFM, FFMM, FMFM and FMMF.
These can be arranged as possibilities.
MMFF -PQRS, RPQS, PRQS, PRSQ, RPSQ
MFMF -PQRS, RPQS, PRQS, RSPQ
MFFM -PRSQ, RPSQ, RSPQ
FFMM -RSPQ
FMFM - RPSQ, PRSQ
FMMF - PQRS, RPQS, PRQS
Q. No. 3:
The gender of R can be determined, if the siblings in the decreasing order of their ages are :
Answer: B Note that the sequence (in decreasing order of ages of siblings)
can be PQRS, RPQS, PRQS, PRSQ, RPSQ and in terms of gender M,F(male, female): MMFF, MFMF, MFFM, FFMM, FMFM and FMMF.
These can be arranged as possibilities.
MMFF -PQRS, RPQS, PRQS, PRSQ, RPSQ
MFMF -PQRS, RPQS, PRQS, RSPQ
MFFM -PRSQ, RPSQ, RSPQ
FFMM -RSPQ
FMFM - RPSQ, PRSQ
FMMF - PQRS, RPQS, PRQS