Case 80 & 81
There are five machines — A, B, C, D, and E — situated on a straight line at distances of 10 m, 20 m,
30 m, 40 m and 50 m respectively from the origin of the line. A robot is stationed at the origin of the line. The robot serves the machines with raw material whenever a machine becomes idle. All the raw materials are located at the origin. The robot is in an idle state at the origin at the beginning of a day. As soon as one or more machines become idle, they send messages to the robot-station and the robot starts and serves all the machines from which it received messages. If a message is received at the station while the robot is away from it, the robot takes notice of the message only when it returns to the station. While moving, it serves the machines in the sequence in which they are encountered, and then returns to the origin. If any messages are pending at the station when it returns, it repeats the process again. Otherwise, it remains idle at the origin till the next message(s) is(are) received.
80. Suppose on a certain day, machines A and D have sent the first two messages to the origin at the
beginning of the first second, and C has sent a message at the beginning of the 5th second and
B at the beginning of the 6th second, and E at the beginning of the 10th second. How much distance
has the robot travelled since the beginning of the day, when it notices the message of E? Assume
that the speed of movement of the robot is 10 m/s.
a. 140 m b. 80 m c. 340 m d. 360 m
Solution
80. a The robot begins to give material to machine A and then to D, it thus covers 40 m in that time span and takes 4 s. Also then it returns to the origin, and takes 4s, while covering 40 m again. When it arrives at the origin, the messages of B and C are already there, thus it moves to give the material to them, which takes it in total 6 s, and it covers 30 + 30 = 60 m in total. Hence, the distance travelled by the robot will be 40 m+ 40 m + 60 m = 140 m.
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81. Suppose there is a second station with raw material for the robot at the other extreme of the line
which is 60 m from the origin, i.e. 10 m from E. After finishing the services in a trip, the robot returns
to the nearest station. If both stations are equidistant, it chooses the origin as the station to return
to. Assuming that both stations receive the messages sent by the machines and that all the other
data remains the same, what would be the answer to the above question?
a. 120 b. 140 c. 340 d. 70
Solution :
81. a In this question, once the robot has delivered the material to machines A and D, it shall reach the origin 2 (nearest), taking 6 s, and covering 60 m. Then it immediately moves to deliver material to machines C and B covering a distance of 40 m and finally back to the origin (nearest). Thus, it cover a distance of 60 m. Hence, it covers a total distance of 120 m.
There are five machines — A, B, C, D, and E — situated on a straight line at distances of 10 m, 20 m,
30 m, 40 m and 50 m respectively from the origin of the line. A robot is stationed at the origin of the line. The robot serves the machines with raw material whenever a machine becomes idle. All the raw materials are located at the origin. The robot is in an idle state at the origin at the beginning of a day. As soon as one or more machines become idle, they send messages to the robot-station and the robot starts and serves all the machines from which it received messages. If a message is received at the station while the robot is away from it, the robot takes notice of the message only when it returns to the station. While moving, it serves the machines in the sequence in which they are encountered, and then returns to the origin. If any messages are pending at the station when it returns, it repeats the process again. Otherwise, it remains idle at the origin till the next message(s) is(are) received.
80. Suppose on a certain day, machines A and D have sent the first two messages to the origin at the
beginning of the first second, and C has sent a message at the beginning of the 5th second and
B at the beginning of the 6th second, and E at the beginning of the 10th second. How much distance
has the robot travelled since the beginning of the day, when it notices the message of E? Assume
that the speed of movement of the robot is 10 m/s.
a. 140 m b. 80 m c. 340 m d. 360 m
Solution
80. a The robot begins to give material to machine A and then to D, it thus covers 40 m in that time span and takes 4 s. Also then it returns to the origin, and takes 4s, while covering 40 m again. When it arrives at the origin, the messages of B and C are already there, thus it moves to give the material to them, which takes it in total 6 s, and it covers 30 + 30 = 60 m in total. Hence, the distance travelled by the robot will be 40 m+ 40 m + 60 m = 140 m.
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81. Suppose there is a second station with raw material for the robot at the other extreme of the line
which is 60 m from the origin, i.e. 10 m from E. After finishing the services in a trip, the robot returns
to the nearest station. If both stations are equidistant, it chooses the origin as the station to return
to. Assuming that both stations receive the messages sent by the machines and that all the other
data remains the same, what would be the answer to the above question?
a. 120 b. 140 c. 340 d. 70
Solution :
81. a In this question, once the robot has delivered the material to machines A and D, it shall reach the origin 2 (nearest), taking 6 s, and covering 60 m. Then it immediately moves to deliver material to machines C and B covering a distance of 40 m and finally back to the origin (nearest). Thus, it cover a distance of 60 m. Hence, it covers a total distance of 120 m.
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