505. Combining Groups

Brachos 5:12

Let’s say that two groups ate together in the same building. If part of one group can see part of the other, they may join together to form a single zimmun. If this is not the case, each group forms its own zimmun. If there is one attendant who is serving both groups, they may join together in a single zimmun even if none of them can see the other group, as long as everyone can hear the zimmun leader clearly.

Brachos 5:13

If three people ate together and one of them went outside to the marketplace, he should be called to listen to what they are saying. He may be counted in the zimmun while in the marketplace and thereby fulfill his obligation. Later, when he returns to the house, he should bentch by himself. However, if ten people ate together and one of them left for the marketplace, the zimmun may not be recited until he gets back.