Seeing that you felt like you knew how to do each of those questions, I think that you just have to be that much more careful.

The 50 to 51 scorer is very comfortable with the different problem types and can be very careful to always answer the correct question, to always keep things like zero and non-integers in mind and be sure not to make any assumptions, especially on Data Sufficiency.

It is possible to feel like you can do the problem, to understand exactly how to do it, but forget a small detail, again especially on Data Sufficiency.

Do your practice tests show you anything? Did you miss DS more than PS? On your practice tests did you even miss questions that you felt like you had answered correctly?

The GMAT does not go beyond a certain complexity of topics and concepts on either the verbal or the Quant, instead they just make it more likely that someone will make a mistake.

Does that make sense?

David,

Thank you very much for your response. I had problems like the one you mentioned where I used to overlook a small little critical words such as "integer", I think I have cured that now.

I have completed all the official gmat material out there from gprep question pack to OG 9 through 13 to supplements. I know no matter how many times you repeat those OGs, you will always find information, but how do you think I should proceed in my next preparation? What should I do? Any insights would be really helpful.

Thanks,
BC