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# If Danielle ran a race at a constant speed, at what time did she finis

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Math Expert
Joined: 02 Sep 2009
Posts: 47983
If Danielle ran a race at a constant speed, at what time did she finis  [#permalink]

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08 Jul 2018, 23:45
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Difficulty:

15% (low)

Question Stats:

79% (00:55) correct 21% (01:10) wrong based on 62 sessions

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If Danielle ran a race at a constant speed, at what time did she finish?

(1) Danielle started the race at 8:00 a.m.

(2) At 9:30 a.m. Danielle was halfway through the race, and at 10:00 a.m., she was 2/3 of the way through the race.

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Math Expert
Joined: 02 Aug 2009
Posts: 6553
If Danielle ran a race at a constant speed, at what time did she finis  [#permalink]

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09 Jul 2018, 00:15
1
If Danielle ran a race at a constant speed, at what time did she finish?

(1) Danielle started the race at 8:00 a.m.
insuff

(2) At 9:30 a.m. Danielle was halfway through the race, and at 10:00 a.m., she was 2/3 of the way through the race.
now we have a time frame 10:00 am - 09:30 am AND also the fraction of race completed = $$(\frac{2}{3}-\frac{1}{2})$$ of total
So (2/3-1/2)=1/6 in half an hour and full in 6*1/2=3hrs
Since half the race at 0930, another 3/2 hrs to complete it.. thus 0930+0130=1100
so suff
B
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Intern
Joined: 17 Jan 2017
Posts: 14
Re: If Danielle ran a race at a constant speed, at what time did she finis  [#permalink]

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09 Jul 2018, 00:28
Let us look at:
Statement 1: At what time Danielle started wouldn't totally help in answering at what time would she finish. So, straight-way, this option ain't sufficient. Eliminate A and D. Although this information might be useful further, let's see...

Statement 2: At 9:30 a.m. Danielle was halfway through the race, and at 10:00 a.m., she was 2/3 of the way through the race.
Let us assume the total distance of the race to be D.
Statement implies that in 30 mins (9:30 a.m.-10:00 a.m.) Danielle covered the distance = (2/3)D-D/2=D/6.
I.E.
1) D/6 distance in 30 mins
2) Danielle had covered D/2 by 9:30 AM, and hence had to cover the next D/2. Using 1) above, D/2 would be covered in 90 mins. Therefore 9:30 AM plus another 90 mins = 11 AM.
So, Danielle will complete the race by 11 AM.

HENCE Statement 2 suffices. Therefore, answer is B. Hope this was useful.
Happy preparing. Good Luck!
Senior Manager
Joined: 14 Dec 2017
Posts: 453
Re: If Danielle ran a race at a constant speed, at what time did she finis  [#permalink]

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09 Jul 2018, 00:36
Bunuel wrote:
If Danielle ran a race at a constant speed, at what time did she finish?

(1) Danielle started the race at 8:00 a.m.

(2) At 9:30 a.m. Danielle was halfway through the race, and at 10:00 a.m., she was 2/3 of the way through the race.

At what time Danielle finishes the race?

Statement 1: Danielle starts the race at 8 am.

Clearly not sufficient.

Statement 2: Let X miles be the Total Distance of the race.

So Danielle finishes a distance of (X/2) - (2X/3) = X/6 miles in 30 mins, since she reached X/2 at 9:30 am & 2X/3 at 10:00 am.

So the time required to finish final X/3 miles = ((X/3) * 30)/(X/6) = (30*6)/3 = 60 mins

Hence the time at which she finished the race = 10:00 am + 60 mins = 11:00 am

Statement 2 is Sufficient.

Thanks,
GyM
Intern
Joined: 26 Feb 2017
Posts: 27
Re: If Danielle ran a race at a constant speed, at what time did she finis  [#permalink]

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15 Jul 2018, 14:12
1
chetan2u wrote:
If Danielle ran a race at a constant speed, at what time did she finish?

(1) Danielle started the race at 8:00 a.m.
insuff

(2) At 9:30 a.m. Danielle was halfway through the race, and at 10:00 a.m., she was 2/3 of the way through the race.
now we have a time frame 10:00 am - 09:30 am AND also the fraction of race completed = $$(\frac{2}{3}-\frac{1}{2})$$ of total
Actually "At 9:30 a.m. Danielle was halfway through the race" is sufficient to answer... half in 0930-0800 or 1hr 30 min , so total in TWICE the time so 3 hrs... time = 08:00 + 3 hrs = 11:00
so suff
B

Hi Chetan ,

B is correct . But in my opinion, you have added information from statement 1 . we dont have any info which says halfway means journey is started at 8 .Please correct me if I am wrong
Math Expert
Joined: 02 Aug 2009
Posts: 6553
Re: If Danielle ran a race at a constant speed, at what time did she finis  [#permalink]

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15 Jul 2018, 18:06
ashisplb wrote:
chetan2u wrote:
If Danielle ran a race at a constant speed, at what time did she finish?

(1) Danielle started the race at 8:00 a.m.
insuff

(2) At 9:30 a.m. Danielle was halfway through the race, and at 10:00 a.m., she was 2/3 of the way through the race.
now we have a time frame 10:00 am - 09:30 am AND also the fraction of race completed = $$(\frac{2}{3}-\frac{1}{2})$$ of total
Actually "At 9:30 a.m. Danielle was halfway through the race" is sufficient to answer... half in 0930-0800 or 1hr 30 min , so total in TWICE the time so 3 hrs... time = 08:00 + 3 hrs = 11:00
so suff
B

Hi Chetan ,

B is correct . But in my opinion, you have added information from statement 1 . we dont have any info which says halfway means journey is started at 8 .Please correct me if I am wrong

Yes, you are correct. Since the statement II was sufficient, I just added extra bit of info that was given in statement I.
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Re: If Danielle ran a race at a constant speed, at what time did she finis &nbs [#permalink] 15 Jul 2018, 18:06
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