The important thing in the question is the order , if you spot this then no need to expand
order is abcabc I can write it as-----abc~abc ( two groups) the group to the left is 1000 times the group to the right
let abc = p
in other words abcabc = 1000p +p = 1001p , so if you know the factors of 1001 you know the answer what are the factor of 1001 ?
we know 11 is a factor ( 11*91) so are 7 and 13 (91=7*13)
Hence the answer is 13
what I see is that when one gets a question similar to this one it should be answerable with in 1 min so there must be a catch to the question
just think why did the question say abcabc ---- because something is there
If you see this the question becomes very easy
