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# Al and Barb shared the driving on a certain trip.

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SVP
Joined: 06 Sep 2013
Posts: 1720
Concentration: Finance
Al and Barb shared the driving on a certain trip.  [#permalink]

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20 Sep 2013, 15:21
3
8
00:00

Difficulty:

35% (medium)

Question Stats:

66% (01:27) correct 34% (01:26) wrong based on 364 sessions

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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.
(2) Al's average driving speed for the entire trip was 4/5 of Barb's average driving speed for the trip.
Math Expert
Joined: 02 Sep 2009
Posts: 51259
Re: Al and Barb shared the driving on a certain trip.  [#permalink]

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20 Sep 2013, 17:09
1
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.
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Joined: 17 Nov 2013
Posts: 90
Re: Al and Barb shared the driving on a certain trip.  [#permalink]

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02 Apr 2016, 08:16
the way i did it is as follows:

1) r x t = d . I was a little confused about the wording "Al drove for 3/4 as much time as Bard did" sounded to me like I needed to add 3/4 to 1. Meaning 4/4 + 3/4 = 7/4 was the answer I got initially as Al's time. But i agree that the correct way to read the stmt is as 3/4 = Al's time. in my formula r x t = d=> r x 3/4t => i don't know what % of the distance the 3/4t covers, i also don't know the rate at which Al is going, plus i don't know how it relates to Barb, i need more information to make this stmt suffice => insufficient.

2) r x t = d => 4/5r x t => Similar to stmt1, I need more information. insufficient.

Combined. for Al we have the rate and the time => 4/5r x 3/4t = 3/5rt. this formula is in direct comparison to Barbs's => r x t = rt => 3/5 rt + rt =8/5rt => Al's distance over the total distance is => 3/5rt / 8/5rt => 3/8 of the distance. Sufficient! Al drove 3/5th as much as Barb did, meaning that he drove 3/8 of the trip.
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Joined: 02 Jul 2016
Posts: 108
Al and Barb shared the driving on a certain trip.  [#permalink]

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30 Jun 2018, 07:23
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
Math Expert
Joined: 02 Sep 2009
Posts: 51259
Re: Al and Barb shared the driving on a certain trip.  [#permalink]

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30 Jun 2018, 09:41
1
suramya26 wrote:
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

No. Say you drive twice as fast as I do. Can we say that you cover twice as much distance as I do? No, because we don't how long each of us drives. If you drive for 1 hour and I drive for 100 hours, what fraction of the total distance drive?
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Re: Al and Barb shared the driving on a certain trip. &nbs [#permalink] 30 Jun 2018, 09:41
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# Al and Barb shared the driving on a certain trip.

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