Final answer:
To go from the first network to the fourth in a series of four networks connected by three routers, a packet would make three hops.
Step-by-step explanation:
If you have four networks connected with three routers in series and you are on the first network trying to send a packet to the fourth network, you must account for the routers that act as intermediaries. Since the routers are in series, each one will represent a 'hop' when a packet is transmitted from one network to the next. Starting from the first network, the packet will first go to the second network (first hop), then to the third network (second hop), and finally arrive at the fourth network (third hop).
Therefore, the packet would travel through three hops to go from the first network to the fourth network. This type of networking question relates to understanding how packets traverse multiple linked networks.