ORIGINAL: Rick James
It's proper, just make sure people in your group are OK with it, make sure other groups can't hear, and make sure no one in your group turns in a card.
I'll second that. I have shot in tourneys where that was allowed. Not all people can afford a range finder and clubs are often very considerate of new archers. Just think of the time spent if every new archer had to guess the yardage. Think of how many arrows would go sailing over the target and the time spent to find those arrows.
Everyone in the group should be comfortable with this concept so don't be afraid to ask.