Score:0

# Will cars arrive to 2nd booth before all cars serviced at first booth?

Suppose cars now “propagate” at 1000 km/hr and suppose toll booth now takes one min to service a car. It's also given each booth is 100 Km apart from previous booth (taken from Computer Networking: A Top-Down Approach, Jim Kurose, Keith Ross):

Question: Will cars arrive to 2nd booth before all cars serviced at first booth?

I answered yes, but the answer I got is, "after 7 min, first car arrives at second booth; three cars still at first booth". I am not sure why that is the case. If propagation speed is 1000 km/hr and length of link is 100 km, then we can see that propagation delay is 100/1000 = 1/10 km/h. So, how do we find that after 7 minutes first car arrived and 3 still at booth 1 please? Here we can imagine booth as a router, caravan as packet and car as a bit.

100 km at 1000 km/h takes 1/10 of an hour or 6 minutes. Add 1 minute for the toll booth.
@AlexD. Thank you, but why we will have 3 cars left at toll booth 1 after 7 minutes please?
It takes 1 minute to service a car. In 7 minutes only 7 cars out of 10 will be serviced.