Brain Teaser – December 3, 2016

Answer: First, the pharmacist fills the 5 ml container with the medicine and pours its contents into the 3 ml container, which he empties afterward.

Then he pours the remaining 2 ml of medicine from the 5 ml container into the 3 ml container.

Next, he refills the 5 ml container with more medicine and carefully pours the medicine from it to fill the 3 ml container (where there is already 2 ml).

This will only require 1 ml from the 5 ml container.

Thus he is left with 4 ml in the 5 ml container, as requested.