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30 Mar 2026, 10:59
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
37% (03:48) correct
63%
(03:46)
wrong
based on 27
sessions
History
Date
Time
Result
Not Attempted Yet
At a certain time, Colleen leaves a point and travels along a straight road at 12 kilometers per hour. Thirty minutes later, Dolly leaves the same point and travels along the same road at 18 kilometers per hour. One hour after Colleen departs, Elaine leaves the same point and travels along the same road at 30 kilometers per hour. If each person travels at a constant speed, how many minutes elapsed between the first meeting of two people and the last meeting of two people?
(A) 10
(B) 15
(C) 20
(D) 30
(E) 40
(A) 10
(B) 15
(C) 20
(D) 30
(E) 40
arushi118
Joined: 21 Jul 2024
Last visit: 24 Apr 2026
Posts: 267
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Concentration: Leadership, General Management
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04 Apr 2026, 01:25
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Imagine that C leaves at 5AM
D will then leave at 5:30AM
DIstance travelled by C till 5:30 = 6KM
They meet in time: 6/(18-12) = 1 hour -- using relative speed -- so they meet at 6:30AM
E leaves 1 hour after C leaves -- so she leaves at 6AM
DIstance travelled by C from 5AM to 6AM = 12KM
Time taken by E and C to meet = 12/18 = 40 mins
So E and C meet at 6:40
DIstance travelled by D in from 5:30AM to 6AM = 9KM
Time taken by E and C to meet = 9/12 = 45 mins
So E and C meet at 6:45
So, the first meeting is at 6:30AM
and the last meeting is at 6:45AM
-- DIfference between these = 15 minutes.
ANs = B
D will then leave at 5:30AM
DIstance travelled by C till 5:30 = 6KM
They meet in time: 6/(18-12) = 1 hour -- using relative speed -- so they meet at 6:30AM
E leaves 1 hour after C leaves -- so she leaves at 6AM
DIstance travelled by C from 5AM to 6AM = 12KM
Time taken by E and C to meet = 12/18 = 40 mins
So E and C meet at 6:40
DIstance travelled by D in from 5:30AM to 6AM = 9KM
Time taken by E and C to meet = 9/12 = 45 mins
So E and C meet at 6:45
So, the first meeting is at 6:30AM
and the last meeting is at 6:45AM
-- DIfference between these = 15 minutes.
ANs = B
04 Apr 2026, 01:45
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First meet happens at 1.5 hrs.
By which team 3rd person travelled for 30mins = 15kms.
The first 2 meet at 18km mark.
Distance now to cover = 3km.
Notice that last meet is when the fastest person meet the second fastest person = 18km/hr speed guy.
Thus 3/30-18 = 3/12hrs = 15 mins which is the gap between first and last meet.
Answer: Option B
By which team 3rd person travelled for 30mins = 15kms.
The first 2 meet at 18km mark.
Distance now to cover = 3km.
Notice that last meet is when the fastest person meet the second fastest person = 18km/hr speed guy.
Thus 3/30-18 = 3/12hrs = 15 mins which is the gap between first and last meet.
Answer: Option B
kevincan
