I had a good turn up to the session I presented; these are primary and secondary
maths teachers from around the state. In this photo they're trying to
work out how many tennis balls will fit into the room. Although the answers were
all different, they were all of the order of 2 million or so (well, they ranged between half
a million and 4 million, and that's actually a not too bad range (it tells us that the answer
isn't up in the tens of millions, or down in the low hundreds of thousands)).