IR Question from GMATPrep

[Kevinst]

Hey,

please look at the IR question posted here:
https://www.beatthegmat.com/graphics-in ... 09048.html

According to the solution in GMATPrep, the _beginning_ of the Cambrian Period marks the onset of a new era, eon and period.
While it is obvious that it marks the onset of a new period, it isn't clear to me why it should also mark the onset of a new eon and era. According to the provided graphic, its _end_ marks the onset of a new era and eon, but its beginning still lies within another era and eon.

Any thoughts?

Thank you,
Kevin

[vrchen]

Hi All,

I am also curious about this question as I came to the same conclusion as Kevinst.

The answer I selected was Precambrian eon as it marks the end of the Paleozoic era which I equate with the start of another (unnamed?) era. It also marks the beginning of the of the Vendian period.

Any thoughts on this would be greatly appreciated!

[vrchen]

Hi All,

I just redid the problem and realize the reason the answer is the Cambrian period is because the timeline shows how far in the past each eon/era/period is. Therefore, what looked like the "end" of the Cambrian period is actually the beginning of the period that started ~550 years ago.

I guess I should've taken the hint that the PREcambrian era came before the cambrian period.

Hope this helps!