Bunuel wrote:

Al and Barb shared the driving on a certain trip. What fraction of the total distance did Al drive?

(1) Al drove for 3/4 as much time as Barb did. We don't know their average speeds. Not sufficient.

(2) Al's average driving speed for the entire trip was 4/5 of Barb's average driving speed for the trip. We don;t know the times. Not sufficient.

(1)+(2) When combined we have all we need:

Barb's time = t hours, Al's time = 3/4*t hours.

Barb's speed = r miles per hour and Al's rate = 4/5*r miles per hour.

Barb's distance = rt and Al's distance = 3/5*rt --> Al's covered (3/5*rt)/(rt+3/5*rt)=3/8 of the total distance. Sufficient.

Answer: C.

Hi Bunuel

Great explanation.

I had a doubt that since we know that time is proportional to distance if the time taken by Al is 3/4 of the time of B, can't we infer from here that the ratio of there distances is 3/4 and Al drove 3/7 of the total distance??????

Thanks in advance