Hi

When we have a question wherein there is a requirement to test for EVEN number..
Shld we consider " 0 " as even and test conditions.
i have done this many times especially in DS sums and have hit on the correct answer..

* yes, 0 is even. also, -2, -4, etc. are even, too.

* the o.g. will NEVER directly test this fact. i.e., the "textbook" method to solve an o.g. problem will not require direct knowledge of the fact that 0 (or -10 etc.) is even.

HOWEVER,
* if you PLUG IN YOUR OWN NUMBERS to solve a problem, you may encounter this issue. if so, then make sure that you know what's even and what's not.

As I came across a problem of OG 12 wherein it was asked to find out sum of all even numbers from 99 to 300. Here, the soln. states that 300 is 150th Even number.. But here we arent considering " 0 " as even...

What am I missing here ??

you don't need to establish whether 0 is even to find this sum, since 0 is not part of the sum.

as for "300 is the 150th even number", this is just a simple convention meant to help you count the evens in the list.
if you started the list with 0 as the "first" even number, then 300 would be the 151st even number, and the problem would become needlessly complicated.