Gmat Prep Please Help: Equal amount of water

I am so tempted to say 1/2 here, but I'm afraid I'm getting it wrong because that would make it really easy. Here is my explanation, please do tell me if I'm wrong...
Since equal amounts of water were poured in two jars, then it is obvious that the bigger jar would be the one with the smaller proportion of "fullness": jar 1/4. If you empty the other jar in this one, you get twice the amount of water initially poured, which will make the bigger jar 2/4 = 1/2 full.

Answer: A.

However, I'm not sure I'm right. It would be suspiciously easy...

The correct answer is A!

My apologies. I read the answer incorrectly. I was suspicious as well and took a complex approach as I thought 1/2 can't be right but 1/2 is correct hey.

Thank you again.

Another easier way to solve such problems is by plugging numbers.

Since Jar A is 1/3rd full with water and Jar B is 1/4th full with an equal amount of water, we could choose a common multiple of 3 and 4 which would be 12.

12 lts of water added to Jar A would make it 1/3 rd full
Total capacity of Jar A = 36

12 lts of water added to Jar B would make it 1/4 th full
Total capacity of Jar B = 48

12 lts of water are taken from Jar A and poured into Jar B which would make 24 lts of water in Jar B while it has a total capacity of 48 lts.

So, fraction of water filled in the larger jar is 1/2.

Excellent explanation guys. Thanks a lot for your time and help