Word problem (my teacher is crazy)

The following is a well known children's rhyme.

As i was going to St Ives,

I met a man with seven wives;

Every wife had seven sacks;

Every sack had seven cats;

Every cat had seven kits;

Kits,cats, sacks, and wives,

How many were going to St Ives?

Often people answer "one" as the rhyme never indicates that anyone else is actually going to St Ives. However, assuming that the entire group is actually going to St Ives show that the answer to the question is in the rhyme sum of a geometric series, and finds its sum.