Question

Suppose there are 12-year old cicadas and those cicadas have predators with 2-year cycles. How often would 12-year cicadas face theirpredators?

Answer 1

It is known that there are 12 year old cicadas and predators have 2 year cycles.

It is said to find how often would the 12 year old cicadas face their predators.

So if the predators emerge in odd years, then they will emerge in year 1,3,5,7,9,11,13,15 and so on.

Hence the 12 year cicadas will never meet the predators if the predators emerge in odd years.

If the predators emerge every even year like years 2,4,6,8,12,...24,...36 and so on then as it is known that the 12 year cicadas will emerge every 12 years so they will emerge in the year 12,24,36 and so on.

So if the predators emerge in even years then the cicadas will encounter the predators every time.