January 29, 2009

Train & tickets



Every station in a rail road issue every other station's ticket.
Some stations are added. Now they have to issue 46 more tickets.
The number of stations before and after addition is ?

4 comments:

  1. If I understand the Q correctly, each station issuing tickets for every other station means that if there are 5 stations, a total of 25 tickets are issued. This will always be a square number.

    There is no difference of squares that equals 46 so the problem as it is stated has no solution. Solutions exist for 44 and 48 more tickets.

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  2. if there are n stations thn total tickets issued =n*(n-1)
    if k no of more station are added
    then tickets issued=(n+k)*(n+k-1)
    the difference of two is 46
    the equation becomes
    (k^2)+(2n-1)(k)-46=0
    solve it for integer values
    initial stations = 11
    additional stations = 2
    total =13 now

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  3. I understand now! A ticket is not for a station of departure but for a particular destination. Hence, a station does not issue its own tickets - only those for other stations to which you can travel.

    11 stations (110 tickets) to 13 (156) is definitely correct.

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  4. i think there will be 23 stations before addition and 24 stations after addition....
    if there are three stations a,b and c
    then total tickets issued in each station equals - 6 - ab,ac,bc,ba,ca,cb
    Now if we add one more station we have to add 6 more tickets - ad,bd,cd,da,db,dc (which is - [current number of stations*2])
    So for 46 new tickets to be added, the current number of stations have to be 23.

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