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Bunuel
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Xavier and Adam are riding motorcycles down the highway at constant 11 Apr 2017, 22:54
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Xavier and Adam are riding motorcycles down the highway at constant speeds. If Xavier is now 2 miles ahead of Adam, how many minutes before Xavier is 3 miles ahead of Adam?

(1) Xavier is traveling at 70 miles per hour and Adam is traveling at 60 miles per hour.
(2) Xavier left 5 minutes before Adam.
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Xavier and Adam are riding motorcycles down the highway at constant Updated on: 13 Aug 2023, 23:52
Originally posted by KarishmaB on 12 Apr 2017, 06:19.
Last edited by KarishmaB on 13 Aug 2023, 23:52, edited 1 time in total.
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Bunuel
Xavier and Adam are riding motorcycles down the highway at constant speeds. If Xavier is now 2 miles ahead of Adam, how many minutes before Xavier is 3 miles ahead of Adam?

(1) Xavier is traveling at 70 miles per hour and Adam is traveling at 60 miles per hour.
(2) Xavier left 5 minutes before Adam.
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Relative Distance = Relative Speed * Time

The relative distance to be covered is 1 mile. We need the time it will take to cover this Relative Distance.

(1) Xavier is traveling at 70 miles per hour and Adam is traveling at 60 miles per hour.
Relative Speed = 70 - 60 = 10 mph
We have the relative distance and relative speed so we can find the time taken.
Sufficient.

(2) Xavier left 5 minutes before Adam.
We know that Xavier left 5 mins before but we don't know for how long Adam has been riding. So we do not know in how much time Xavier covered a relative distance of 2 miles.
Say both have the same speed so their relative speed is 0. In that case, Xavier would have covered the 2 extra miles in 5 mins.
Say Xavier covered 1 mile in 5 mins and hence has a speed of 12 mph. If Adam's speed is 2 mph, Xavier would have covered another 1 mile extra in 6 mins.
In either case, their relative speed is different and hence, time taken for Xavier to cover a relative distance of 1 mile will be different.
Not sufficient.

Answer (A)

Check this video for when to use relative speed: https://youtu.be/wrYxeZ2WsEM
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Xavier and Adam are riding motorcycles down the highway at constant Updated on: 12 Apr 2017, 08:32
Originally posted by mohshu on 12 Apr 2017, 05:32.
Last edited by mohshu on 12 Apr 2017, 08:32, edited 1 time in total.
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stat1 : relative velocity = 10 miles per hour...

so in every 6 minutes the distance grows as 1 mile...

hence in 12 mins 2 miles..
18 mins 3 miles

suff


stat 2 : not suff..

ans A
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Xavier and Adam are riding motorcycles down the highway at constant 03 Jun 2017, 07:40
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VeritasPrepKarishma

so for every question as mentioned only relative speed is required to solve the problem?
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Xavier and Adam are riding motorcycles down the highway at constant 05 Jun 2017, 21:49
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VeritasPrepKarishma

so for every question as mentioned only relative speed is required to solve the problem?
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I am not sure what you mean by "every question as mentioned". But whenever there are two or more people and the question talks about the "distance between them" etc, relative speed comes in handy.
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Xavier and Adam are riding motorcycles down the highway at constant 24 Oct 2017, 11:23
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VeritasPrepKarishma
Bunuel
Xavier and Adam are riding motorcycles down the highway at constant speeds. If Xavier is now 2 miles ahead of Adam, how many minutes before Xavier is 3 miles ahead of Adam?

(1) Xavier is traveling at 70 miles per hour and Adam is traveling at 60 miles per hour.
(2) Xavier left 5 minutes before Adam.

Relative Distance = Relative Speed * Time

The relative distance to be covered is 1 mile. We need the time it will take to cover this Relative Distance.

(1) Xavier is traveling at 70 miles per hour and Adam is traveling at 60 miles per hour.
Relative Speed = 70 - 60 = 10 mph
We have the relative distance and relative speed so we can find the time taken.
Sufficient.

(2) Xavier left 5 minutes before Adam.
We know that Xavier left 5 mins before but we don't know for how long Adam has been riding. So we do not know in how much time Xavier covered a relative distance of 2 miles.
Say both have the same speed so their relative speed is 0. In that case, Xavier would have covered the 2 extra miles in 5 mins.
Say Xavier covered 1 mile in 5 mins and hence has a speed of 12 mph. If Adam's speed is 2 mph, Xavier would have covered another 1 mile extra in 6 mins.
In either case, their relative speed is different and hence, time taken for Xavier to cover a relative distance of 1 mile will be different.
Not sufficient.

Answer (A)
Show more

Hi Karishma,

I have small question regarding statement2 explanation:
can we assume adam speed to be less than or equal to Xavier's?, because the question asks, how much time before was Adam 3 miles behind Xavier, if that were to happen, Adam speed has to be greater than Xavier's to get closer and closer to Xavier to make the question valid. If Adam speed is less than Xavier's , Xavier will be moving away for every minute. Am i correct?

Please clarify

Thanks
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Xavier and Adam are riding motorcycles down the highway at constant 25 Aug 2023, 05:32
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