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03 Jun 2020, 11:08
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
85% (01:55) correct
15%
(02:09)
wrong
based on 66
sessions
History
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Time
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Not Attempted Yet
On the first day of the launch of an anticipated electronic item, a queue formed outside an exclusive electronics store that sold the item. At the time the store opened, the queue had 60 people in it and throughout the day, a new person joined the queue every 3 minutes. That day, the store served, only the people in the queue, at a constant service rate of 30 people per hour. If no person re-joined the queue upon getting served once, how many people were in the queue 4 hours after the store opened?
A. 20
B. 40
C. 60
D. 80
E. 100
A. 20
B. 40
C. 60
D. 80
E. 100
yashikaaggarwal
Senior Moderator - Masters Forum
Joined: 19 Jan 2020
Last visit: 29 Mar 2026
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Location: India
Schools: Cranfield (A) Warwick MiM "23 (M)
GPA: 4
WE:Analyst (Internet and New Media)
03 Jun 2020, 11:32
Kudos
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The queue had 60 people at the time of its opening.
1 new person add on in every 3 minutes
20 new person in an hour
Also the store serves 30 people in an hour and they leave..
So in first hour of shop the queue had the following addition and subtraction.
1st hour : 60+20-30 = 60-10 = 50
2nd hour : 50+20-30 = 50-10 = 40
3rd hour : 40+20-30 = 40-10 = 30
4th hour : 30+20-30 = 30-10 = 20
So after 4th hour. Only 20 people were remaining in the queue.
Answer should be A
Posted from my mobile device
1 new person add on in every 3 minutes
20 new person in an hour
Also the store serves 30 people in an hour and they leave..
So in first hour of shop the queue had the following addition and subtraction.
1st hour : 60+20-30 = 60-10 = 50
2nd hour : 50+20-30 = 50-10 = 40
3rd hour : 40+20-30 = 40-10 = 30
4th hour : 30+20-30 = 30-10 = 20
So after 4th hour. Only 20 people were remaining in the queue.
Answer should be A
Posted from my mobile device
03 Jun 2020, 12:02
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Bunuel
Total number of people in the quere 4 hours after the store opened
= Initial number of people in the queue (at time t=0) + Total number of people that became a part of the queue in those 4 hours - Total number of people served
Let's try to calculate the values of these variables.
The number of people in the queue at the time when the shop opened = 60 (given)
Every three minutes, a new person was added to the queue. We have to find the total number of people added in 4 hours (4*60 = 240 minutes)
Therefore, number of people added in the queue in 240 minutes = 240/3 = 80 people (Because a new person is added every 3 minutes)
Now, total number of people served in 4 hours = Rate at which people are served * 4 hours
= 30*4 = 120 people
Hence, Total number of people in the queue 4 hours after the store opened = 60 + 80 - 120 = 140 - 120 = 20
The answer is (A)
