questions in OG11 are arranged in order of increasing difficulty.

In genreal, you will find last one fifth questions in each section of this book, most difficult.
and the book starts with easy problems.

WHat else you wanna know?

since the q is raised, i referred to OG11 whether they have mentioned it clearly or not. Unfortunately they havent discussed about the OG11 book in the book at all.
isnt it ironic? dont you think
.......................

i think the same query been discussed somewhere
i dont remember where so i am explaining it once again, otherwise i d recommend you to read all topics in strategy section first.

you wanna check https://www.beatthegmat.com/viewtopic.php?t=636
good discussion there.