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19 Dec 2025, 13:09
Kudos
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When the robots start they are half a circumference away from each other (let's call it the length of the circumference x). After they meet they are at the same point, so to meet again their cumulative distance (the sum of the distance each of them travels) must be x.
(1) they meet after 26s. it means they walked x/2 in 26 seconds (it does not matter at which speed or which was the fastest). Therefore to walk x, they must take 26s * 2 = 52s.
total time = 52 + 26 = 78.
This information is sufficient to determine a unique value for how many seconds it will take for them to meet the second time, so the information is sufficient.
(2) statement 2 only tells you the ratio of the robots' speed but this is not sufficient to determine one unique value for the number of seconds it takes them to meet, for example the speeds could be 3mph and 4mph, or 6mph and 8mph, etc.
Even without knowing the length of the circumference, it's easy to understand that it's impossible to determine the robots' exact speed.
answer A
(1) they meet after 26s. it means they walked x/2 in 26 seconds (it does not matter at which speed or which was the fastest). Therefore to walk x, they must take 26s * 2 = 52s.
total time = 52 + 26 = 78.
This information is sufficient to determine a unique value for how many seconds it will take for them to meet the second time, so the information is sufficient.
(2) statement 2 only tells you the ratio of the robots' speed but this is not sufficient to determine one unique value for the number of seconds it takes them to meet, for example the speeds could be 3mph and 4mph, or 6mph and 8mph, etc.
Even without knowing the length of the circumference, it's easy to understand that it's impossible to determine the robots' exact speed.
answer A
19 Dec 2025, 13:42
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Bunuel
IMO A
They start diametrically opposite hence C/2 where C is circumference is the distance travelled before meeeting
Time of meeting = c/2/speed first robot + speed of second robot .
Option 1 - 26=c/2 / s1+s2 .. which can be written as 52=c/s1+s2....
at the second meeting they would have travelled the entire circumference of the track hence C=52. hence time of meeting second time after strating = 52+26=78 sufficient
Option 2 - All we know is v1=3/4 v2. with which we cant do pretty much nothing. hence insufficient.
Hence A
19 Dec 2025, 13:55
Kudos
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Let circumference of corridor be C, speed of both robots be v1 and v2 resp.
As they are moving towards each other, their relative speed is v1+v2
and since they started diametrically opposite, they need to cover a distance of C/2 together to first meet.
t1 = (C/2)/(v1+v2)
To meet for the second time, they need to cover total of 3C/2 since they started.
t2 = (3C/2)/(v1+v2) = 3*t1
(1) As t1 = 26, t2 would be its 3 times. Hence, sufficient alone.
(2) v1 = 3/4 v2
t2 = (3C/2)/(v1+3/4v2)
t2 cannot be identified as there are unknowns. Not sufficient alone.
The answer is (A)
As they are moving towards each other, their relative speed is v1+v2
and since they started diametrically opposite, they need to cover a distance of C/2 together to first meet.
t1 = (C/2)/(v1+v2)
To meet for the second time, they need to cover total of 3C/2 since they started.
t2 = (3C/2)/(v1+v2) = 3*t1
(1) As t1 = 26, t2 would be its 3 times. Hence, sufficient alone.
(2) v1 = 3/4 v2
t2 = (3C/2)/(v1+3/4v2)
t2 cannot be identified as there are unknowns. Not sufficient alone.
The answer is (A)
