Joy Shaha wrote:A technician makes a round-trip to and from a certain service center by the
same route. If the technician completes the drive to the center and then
completes 10 percent of the drive from the center, what percent of the
round-trip has the technician completed?
A) 5%
B) 10%
C) 25%
D) 40%
E) 55%

We can use the answer choices to our advantage (ALWAYS check the answer choices before performing any calculations - see the General GMAT Math Strategies video below)

The TOTAL distance for the round trip = (distance from home to service center) + (distance from service center to home)
Once the technician drove the distance from home to service center, he/she has completed HALF (50%) of the round trip.

Once the technician drives a portion of distance from service center to home, he/she has completed more than HALF of the round trip.

So, the correct answer is GREATER THAN 50%

Answer: E

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Joy Shaha wrote:A technician makes a round-trip to and from a certain service center by the
same route. If the technician completes the drive to the center and then
completes 10 percent of the drive from the center, what percent of the
round-trip has the technician completed?
A) 5% B) 10% C) 25% D) 40% E) 55%

We can let the distance to the center = d, so the roundtrip distance = 2d.

Since the technician has driven to the center and completed 10 percent of the drive home, he has gone d + 0.1d = 1.1d. Thus, the percent completed is:

(1.1d)/(2d) x 100

11/20 x 100 = 11 x 5 = 55 percent.

Alternate solution:

As Brent has already mentioned, after the technician has driven to the center, he or she has completed half, or 50% of the round trip. We know that the technician will drive a bit more, and without doing the math, we see that the only logical answer choice is 55%.

Answer: E

Hi All,

Certain Quant question on the GMAT are really just 'logic' questions - and don't actually require much (if any) math to solve. You have to pay careful attention to what you're told - and taking the necessary notes, drawing a picture, etc. will help make answering those questions even easier. Here, we're asked to think in terms of the ROUND-TRIP (meaning to the service center and back via the same route). We know that the worker got to the center, so that's 50% of the trip right there. Any additional travel (in this case, 10% of the way back) would only INCREASE the percent of the round-trip that the worker took. Thus, the answer MUST be greater than 50% - and there's only one answer that 'fits.'

Final Answer: E

GMAT assassins aren't born, they're made,
Rich