I was asked this question during an interview. Just would like to verify whether my answer is correct.
Q: How many DRs in an area?
A: 1 DR per vlan or per subnet.
First of all, a DR for a multiaccess network can be elected only from among routers that are directly connected to that network. The routers that are not directly connected to that multiaccess network have nothing to do with that or with DR elections for that segment. Therefore, we say that the DR is not a function of the entire router but rather a function of each of its interface. A router can be DR in one multiaccess network, a BDR at the same time in some other network, and in yet some other network, it may be DROTHER (i.e. not DR nor BDR). Okay?
Now, I assume that you are asking about the following topology:
Ethernet <---> Router1 <---> Point-to-Point <---> Router2 <---> Ethernet
If there are 5 VLANs on each Ethernet then there are 10 VLANs in total. Each of these VLANs has to have its own DR. As the Ethernet VLAN is considered to be a multiaccess-type network, there will be 10 DRs in this area (note that both the Router1 and Router2 will be DRs for the VLAN they are connected to because they are the only router on that VLAN so far so they will be automatically elected as DR). Both Router1 and Router2 will be 5-fold DRs - for each VLAN they are connected to.
However, if the situation was different, like this:
Router1 <---> Common backbone network
Router2 <---> Common backbone network
Router3 <---> Common backbone network
and all other interconnections in this network, including to routers not displayed here, were only point-to-point and no other multiaccess network was present, there would be only a single DR in this area because there is only a single multiaccess network here. The DR would be elected from among Routers 1-3 first depending on their priority and the according to their Router ID (the highest wins).