Shirsendu Roy

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  • in reply to: Divisibility #66788
    Shirsendu Roy
    Spectator

    a1,a1+a2,.....,a1+a2+...a100

    if any one of these 100 terms divisible by 100 then we are through.

    otherwise suppose that none of them is divisible by 100, then each leaves a remainder 1,2,...99. Since there are 100 sums and 99 remainder, by Pegion hole principle PP1, two of the sums leaves the same remainder after division by 100,

    then let a1+a2+....+am=b100+r

    a1+a2+....+an=c100+r

    That gives m<n, a_{m+1}+a_{m+2}+....+a_{n}=100(c-b)

    or, 100 divides a_{m+1}+a_{m+2}+....+a_{n}.

    in reply to: Algebra #66674
    Shirsendu Roy
    Spectator

    this number has least value compared to the other numbers given here.

    in reply to: Algebra #66673
    Shirsendu Roy
    Spectator

    97yz-97z-97=19xyz equation A

    here 97-z-1 <yz

    or, yz-z-1 <yz

    or, 97(yz-z-1)<97yz

    or,19xyz <97yz

    or, 19x <97

    or, x<97/19

    or, x=1,2,3,4,5 is equation B

    gcd(19,97)=1

    or,at least one of x,y,z is multiple of 97 not=x

    let y=97m

    or, 97(97mz-z-1)=19x97mz

    or,(97mz-z-1)=19xmz

    or,(97-19x)mz=z+1  is equation C

    here (97-19x)>=2 since x=1,2,3,4,5

    (97-19x)mz>=2mz>=2z>z+1

    and we have a contradiction with C

    or, y cannot be multiple of 97

    then let z=97m then A

    becomes 97(y97m-97m-1)=19xy97m

    or,97ym-97m-1=19xym

    or,(97y-97-19xy)m=1 is equation D

    since these are positive integer quantities, D implies that both m and 97y-97-19xy=1, m=1 or, z=97

    or, 97y-19-19xy=1

    or,97y-19xy=98

    or,(97-19x)y=98

    or,y=98/(97-19x)

    where from A we get 97-19x=78,59,0,21and 2 for x=0,1,2,3,4,5

    since y is positive integer, it follows that the first four values not taken, x=5,97-19x=2,y=49,z=97.

    in reply to: Algebra #66663
    Shirsendu Roy
    Spectator

    here (1.001)^1000<2^9<3^6<1000<(1.01)^1000

    largest among numbers (1.01)^1000

    in reply to: INMO 1991 #64136
    Shirsendu Roy
    Spectator

    The question may have some modifications please upload screenshot of original question

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