# Linear Thinking and Data Sufficiency

Very often, the Quant section on the GMAT isn’t about math at all, but rather about common sense and the right approach.

Take a look at the following problem from the *Official Guide* (12th edition, p. 284, Q130):

If Juan had a doctor’s appointment on a certain day, was the appointment on a Wednesday?

(1) Exactly 60 hours before the appointment, it was Monday.

(2) The appointment was between 1:00pm and 9:00pm.

As you have probably surmised, there’s no need for fancy math here. The catch lies in the form of linear thinking.

When reading the question stem, most test takers have a vision of Juan entering his doctor’s office. In our vision, the sun is shining on Juan as he enters the cool, air-conditioned waiting room between 9:00am and 5:00pm. This sort of image is hard to shake, which is exactly what our friends at the GMAT are counting on.

So when we read statement (1), we’re unconsciously thinking “Monday morning/afternoon.” If we then add 60 hours (twice 24 hours plus an extra 12 hours, or 2 1/2 days), we’ll find ourselves on Thursday evening, not Wednesday.

Now the significance of the 60 hours becomes clear: If we begin the 2 1/2 day period on Monday at 1:00 AM, Juan will have the appointment at 1:00pm on Wednesday afternoon (add two days to reach Wednesday 1:00am, then add half a day), and the answer is “yes.” But if we begin the 2 1/2 day period 12 hours later on Monday 1:00 PM, then the appointment will also occur 12 hours later – at 1:00am, Thursday, and the answer is “no.” Thus, statement (1) alone is insufficient.

When moving to statement (2), watch out for linear thinking again. Statement (2) ALONE doesn’t tell you on which day the appointment was scheduled. You need both statements to stand a chance to fix the schedule on Wednesday. And fix it they do: for the appointment to be at 1:00pm, the 2 1/2 day period needs to start at 1:00am two days earlier.

Likewise, for the appointment to be scheduled at 9:00pm (eight hours later), the 2 1/2 day period needs to start at 9:00am two days earlier. If, according to statement (1), that day is a Monday, then the appointment MUST be sometime between 1:00pm and 9:00pm on Wednesday, and the answer is a definite “yes,” or sufficient.

As strange as it may sound, you don't always need a specific formula or calculation to solve Quant problems on the GMAT. Common sense and the right approach are powerful tools as well!