GMAT: Data Sufficiency
Not what you studied in school: Data Sufficiency questions take some getting used to. You are asked not to calculate a value, but to determine whether you can arrive at a unique answer using the information supplied – a yes/no, or Boolean, response.
So abandon your computations at the very moment you realise whether you can (or cannot) complete them
Behavioural factors: Candidates display certain predictable behaviours, which GMAT exploits. They tend to favor the “comfort” of throwing all the available data in the pot in the shape of answer “C”, Similarly answer “E”, stating that the question cannot be answered, feels like failure (it’s not), and so candidates shy away from it. Be aware of these subconscious influences.