Problem 1

A technologically advanced colony of army ants sets out to infiltrate colonies of the rival leaf cutter ants using ant-droids. They already manufactured 250000 ant-droids, each identified by their unique production number between 1 and 250000. However, upon switching them on, the army ants realized that due to an unfortunate programming error, any ant-droid attacked the ant-droids whose identifiers were multiples of their own identifier. The queen ordered the ant-droid army to be divided into smaller units in which no ant-droid wants to attack an other. At least how many units need to be created?

To deter guessing without thinking, we ask that you also solve the following simple arithmetic problem before checking your answer:

What is 6 × 2 - 3?

This problem was first solved on Wed 24th January at 4:05:42pm