A room has 50 lockers all closed. There are 50 people waiting outside tje room.The first person goes in and opens all lockers, the second person goes in and closes lockers which are multiple of 2,the third person change the state of all the lockers whuch are multiple of 3, till 50. How many lockers are closed ?

(a)32 (b) 25 (c) 43 (d) None of these.


If you know this answer , please reply to me immediately.

Bye
Suprovo.

None of these :twisted:
:roll:

A room has 50 lockers all closed. There are 50 people waiting outside tje room.The first person goes in and opens all lockers, the second person goes in and closes lockers which are multiple of 2,the third person change the state of all the lockers whuch are multiple of 3, till 50. How many lockers are closed ?

(a)32 (b) 25 (c) 43 (d) None of these.


If you know this answer , please reply to me immediately.

Bye
Suprovo.


Hi, there are 19 lockers closed after third person changes the state of the same

The Answer is None of These, and here is the solution.....if you do some calculation with pen and paper then you will come to see a unique trend of the gates which are left open.....it comes out that the gate numbers ...... 1^2, 2^2, 3^2, 4^2, 5^2, 6^2, and 7^2 will remain open.....so these come out to be 7 in all which will remain open after the 50 person has done his job.
hope that I am clear :shock:

<sarsij>

My guess is :roll: B.) 25

2 * 25 = 50 (we need multiples of 2 right...) that means 25 doors open & 25 closed. So the SECOND person closes 25 of the 50 doors.

3 * 16 = 48 (we need multiples of 3) that means the state of 16 doors changes. But we need to know how many of these 16 will be open doors & how many will be closed doors.

So we need to consider common multiples of 3 & 2
if you do (3*2) * 8 = 48

1.) it gives us the 8 doors that the THIRD person will open which SECOND person has closed.
2.) and 8 open doors will be closed by the THRID person.

So if you observe the THIRD person is opening 8 and closing 8 doors, therefore the state of doors remain exactly the way it was after the SEOND person i.e 25 open & 25 closed

So now you know the answer...hope that's the right logic.... :P