Let's look at this vacuum cleaner issue

Since the salesman assured the lady that this vacuum cleaner cuts the work in half, she assumed that the purchase and usage of a second cleaner would finish the whole job.
However, the second vacuum again would cut the remaining work in half, so a third cleaner would again cut the work in half, and so on and so on, each vacuum would only cut the remaining job in half until the lady purchases an infinite number of vacuum cleaners.
( The Hoover Comp. would love this lady.)

Bertstravels 
is reminded of the Greek Philosopher Zeno
and his theory of Achilles and the turtle.