english math questions

hi, everyone, you may be surprised to find out that i write the math questions in the Communication Field, but i really don't know where i can ask this math problem in other sections, please help me

it is a AMC contest questions

a finite sequence of three - digit integers has the property that the tens and units digits of each term     are, respectively, the hundreds and tens digits of the next  term, and the tens and units digits of the last term are , respectively, the hundreds and thens digits of the first term. for example, such a sequence might begin with terms 247, 475, and 756 and end with the term 824. Let S be the sum of all the terms in the sequence. what is the largest prime number that always divide S?

a. 3
b. 7
c. 13
d. 37
e. 43

if you can also tell me where i should go to ask this kind of question next time, i will greatly appreciated it.

thank you

If  the  sequence is ;

a0b0c0  a1b1c1  a2b2c2……  anbncn

Then     b0=a1    c0=b1

            b1=a2    c1=b2

            b2=a3    c2=b3

             ……
       bn-1=an   cn-1=bn

And     bn=a0      cn=b0

then    a0+a1+a2+......+an=b0+b1+b2+,,,,,,+bn=c0+c1+c2+,,,,,,+cn

So  S=100(a0+a1+a2+……+an)+10(b0+b1+b2+……+bn)+（c0+c1+c2+……+cn）

    =111(a0+a1+a2+……+an)

       =37×3×(a0+a1+a2+……+an)

The answer should be (d)

[ 本帖最後由 njtianbei 於 2007-2-16 18:56 編輯 ]