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20 Dec 2025, 05:36
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Two autonomous cleaning robots move along a long circular corridor. They start at the same time from points diametrically opposite each other on the corridor, one moving clockwise and the other moving counterclockwise. They continue without stopping at their own constant speeds. After how many seconds after they start do they meet for the second time?
Since the robots move in opposite directions, their relative speed is v1+v2.
And they start from diametrically opposite points, so the initial distance between them is half the circumference of the circular corridor.
(1) They meet for the first time 26 seconds after they start.
First meeting = (C/2)/(v1+v2) = 26 seconds
C/(v1+v2) =26*2 = 52 seconds
First meeting = 26 seconds
Second meeting = 26+52= 78 seconds
It is sufficient
(2) One robot moves at a speed that is 3/4 the speed of the other.
This option does not give actual speeds or distance, so the meeting times cannot be determined.
It is insufficient
A
Since the robots move in opposite directions, their relative speed is v1+v2.
And they start from diametrically opposite points, so the initial distance between them is half the circumference of the circular corridor.
(1) They meet for the first time 26 seconds after they start.
First meeting = (C/2)/(v1+v2) = 26 seconds
C/(v1+v2) =26*2 = 52 seconds
First meeting = 26 seconds
Second meeting = 26+52= 78 seconds
It is sufficient
(2) One robot moves at a speed that is 3/4 the speed of the other.
This option does not give actual speeds or distance, so the meeting times cannot be determined.
It is insufficient
A
20 Dec 2025, 06:00
Kudos
Bookmarks
Two autonomous cleaning robots move along a long circular corridor. They start at the same time from points diametrically opposite each other on the corridor, one moving clockwise and the other moving counterclockwise. They continue without stopping at their own constant speeds. After how many seconds after they start do they meet for the second time?
(1) They meet for the first time 26 seconds after they start.
(2) One robot moves at a speed that is 3/4 the speed of the other.
AD — both robots start moving from opposite points of diameter and moves towards each other, which means they will 1st time when they complete a semicircle together which takes them 26 secs.
To meet second time Robots will have to complete one complete circle which will take them twice of 26 secs since relative speed remains same and distance is twice.
Hence, Sufficient.
B -> let’s consider speed of 1st robot = x then speed of 2nd robot = 3x/4
Relative speed = 7x/4
To find time we need distance which is not given and another variable has to be considered. - Insufficient
Answer -A
(1) They meet for the first time 26 seconds after they start.
(2) One robot moves at a speed that is 3/4 the speed of the other.
AD — both robots start moving from opposite points of diameter and moves towards each other, which means they will 1st time when they complete a semicircle together which takes them 26 secs.
To meet second time Robots will have to complete one complete circle which will take them twice of 26 secs since relative speed remains same and distance is twice.
Hence, Sufficient.
B -> let’s consider speed of 1st robot = x then speed of 2nd robot = 3x/4
Relative speed = 7x/4
To find time we need distance which is not given and another variable has to be considered. - Insufficient
Answer -A
20 Dec 2025, 06:19
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I. When they meet for the first time, they have to cover 1/2 of the circumference which they cover in 26 seconds.
Starting from the 1st meeting point, they keep moving and will now meet after 1 whole round is completed.
If 1/2 round is completed in 26 seconds, 1 whole round will take 52 seconds. They will meet again after 78 seconds.
Hence 1 alone is sufficient.
II. One moves at 3/4 the speed of the other. With this, the relative position of the second meeting can be found, but since the answer is to be given in time for which no information is given, 2 alone is not sufficient
Hence, Option A
Starting from the 1st meeting point, they keep moving and will now meet after 1 whole round is completed.
If 1/2 round is completed in 26 seconds, 1 whole round will take 52 seconds. They will meet again after 78 seconds.
Hence 1 alone is sufficient.
II. One moves at 3/4 the speed of the other. With this, the relative position of the second meeting can be found, but since the answer is to be given in time for which no information is given, 2 alone is not sufficient
Hence, Option A
