Sometimes a group can get off track, or go around in circles, because the different members are actually solving different problems. A good way to head this off is to take some time early on to make sure that everyone agrees on what the group is being asked to do, and what will count as an acceptable answer, e.g.,

A: It says we're supposed to find the ratio of the areas.
A: But is that going to be a number, or a formula?
B: I guess maybe we should try to find a formula...
B: and if there's enough information, we can use it...
B: to find a number.
C: Does it matter which one is on top of the ratio?
A: Well, if we get it one way, we can flip it if we want the other...
A: but maybe we should decide that area will be on top...
A: just so we're all on the same page?