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GMATbuster92
Joined: 28 Jun 2018
Last visit: 20 Jul 2019
Posts: 147
Given Kudos: 32
Location: India
Concentration: Finance, Marketing
Schools: CUHK '21 (II)
GMAT 1: 650 Q49 V30
GPA: 4
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20 Jul 2018, 11:56
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
70% (01:35) correct
30%
(01:46)
wrong
based on 184
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A and B are running in opposite directions on a circular track with radius of 7 miles. If they kept running continuously at their own uniform speeds till they met for the second time, What will be the sum of their respective speeds (miles/hr)?
1) A and B both starts from same point and cover same distance before first meeting.
2) A can cover entire circular track in 10 min.
1) A and B both starts from same point and cover same distance before first meeting.
2) A can cover entire circular track in 10 min.
20 Jul 2018, 20:40
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kshitizbansal92
A and B could have been given car as poor guys ran for almost \(2\pi*r=2*7*22/7=44 miles each\) that too if the speeds were same
Meeting second time mean they have covered 2 laps within themselves, so covered 88 miles
Sum of speed =88/(time taken)
1) A and B both starts from same point and cover same distance before first meeting.
This means the speeds are same but what is the speed not known
2) A can cover entire circular track in 10 min
Now this guy A is super human, as running 44miles in 10 minutes is just awesome. Speed =44/(10/60)=44*6=264 miles per hour.
But we don't know about B.
Insufficient
Combined..
So B also takes 10 minutes and he is also awesome with a speed of 264 miles per hour
Combined speed = 264*2=528 miles per hour .....
I am sure no good source would come up with such statistics
General Discussion
23 Aug 2019, 08:14
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GMATbuster92
What is the question?
Compute the sum of their respective speeds.
When is the data sufficient?
If we get a unique value for the sum of their speeds from the statement(s), the data is sufficient.
Evaluate Statement 1 ALONE: A and B both start from same point and cover same distance before first meeting.
Because they start from the same point (unstated in the question stem and statement but essential to answer - they should have started simultaneously as well) and cover equal distance before their first meeting we can infer that "they run at the same speed'.
However, we do not have a value for their speeds.
So, statement 1 alone is not sufficient.
Evaluate Statement 2 ALONE: A can cover entire circular track in 10 min.
From question stem, we know the radius of the track. We can compute the circumference and hence the length of the track.
From statement 2, we know the time taken by A to cover one lap.
So, we can compute the speed at which A is running along the track.
However, we do not know the speed at which B is running.
So, statement 2 alone is not sufficient.
Evaluate statements together
From statement 1: We know that they run at the same speed.
From statement 2: We know the value of A's speed.
So, we have just found the value of B's speed as well.
Add the two numbers, we have a unique answer.
Statements together are sufficient.
Choice C
Note: Do not waste time computing the values. Just knowing that the value is unique will suffice.
