undergraduate students

[nidhis.1408]

University U has 13,472 undergraduate students, 37.5 percent of whom are upperclassmen. The rest are underclassmen. What percent of its undergraduate students are in the College of Liberal Arts?

(1) The number of upperclassmen who are not in the College of Liberal Arts is three times the number of upperclassmen who are in the College of Liberal Arts.

(2) The number of upperclassmen in the College of Liberal Arts is three times the number of underclassmen not in the College of Liberal Arts.

This problem is from Kaplan gmat cat 1. The explanation given is not very clear.

[user123321]

University U has 13,472 undergraduate students, 37.5 percent of whom are upperclassmen. The rest are underclassmen. What percent of its undergraduate students are in the College of Liberal Arts?

(1) The number of upperclassmen who are not in the College of Liberal Arts is three times the number of upperclassmen who are in the College of Liberal Arts.

(2) The number of upperclassmen in the College of Liberal Arts is three times the number of underclassmen not in the College of Liberal Arts.

This problem is from Kaplan gmat cat 1. The explanation given is not very clear.

1)
- LA NLA
UP x 3x
UN - -

with this information we can get nothing about how many are in liberal arts. hence insufficient.

2)

- LA NLA
UP 3y -
UN - y

with this information we can get nothing about how many are in liberal arts. hence insufficient.

using both tables,
we know that 3y = x
& 3x + x = 0.375*13472

you can get x & y and then can solve entire table.
Once you solve the table, % is easy to calculate. hence sufficient.

IMO C

user123321

[mdavidm_531]

Best to tackle it as a double matrix problem.

Common pitfalls:

1. Solving for 37.5% of 13,472. Remember, this is a data sufficiency problem, which only asks if the data is sufficient for you to solve the problem. If you find yourself solving for (0.375)(13,472) then you fell onto the trap of mechanical thinking. Always think that GMAT is not about hard-nosed solving skills. Solving is contingent to how you think.

2. Not looking at each statement independently. Don't carry over information from statement 1 to statement 2. You are very susceptible to this error especially when transitioning from statement 1 to statement 2 because you tell yourself after evaluating statement 1, "mm hmm, if only there's this additional data then it would be sufficient." And then you proceed to statement 2 and tell yourself, "aha! here's the one I'm looking for in statement 1." And then you answer B. That's a trap! Take into account those two statements.

3. Never be afraid to assign variables. But it would be best to use the fewest variables you can use.