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 in metres 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 metres per second.
Explanation:
Machines A and D sent message at the beginning of the first second.
∴ Round 1: Origin to Machine A to Machine D to Origin
Distance covered by the robot = 80 m (40 m + 40 m)
Time taken to return to origin = 8 seconds
At the end of 8th second, messages from C and B are already received,
∴ Round 2: Origin to Machine B to Machine C to Origin
Distance covered by the robot = 60 m (30 m + 30 m)
Time taken to return to origin = 6 seconds
Total Time elapsed = 8 + 6 = 14 seconds
At the end of 14th second, message from E is already there.
The robot has travelled 140 m (80 m + 60 m), when it notices message from E.
Hence, option (a).
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