OG-17 Problem solving

Hi Joy Shaha,

This question was discussed here:

https://www.beatthegmat.com/og-17-t293465.html

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Rich

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:Q. 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:

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

Joy Shaha wrote:Q. 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%

Had there been an option as 60%, the question would have been interesting.

Say the one-way distance = 100 meters.

Thus, the one round trip = 200 meters

He completed 100 + 10% of 100 = 110 meters.

Or, he completes (110/200)*100% = 55% of the trip.

The correct answer: E

Hope this helps!

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