Now, the answer is that is pedantic 8 yo does not actually need to know whether Sophie is included in the total or not in order to answer the question. i.e. whether Sohpie is a passenger or not.
Now, to me that is blindingly obvious. What puzzled me is not, for a change, trolls on the Internet, but that so many people (indeed, I think all but one) comment that she may be the bus driver and suggesting that matters. One person said to put the answer and "assuming Sophie was driving the bus". It seems almost everyone assumed that it mattered if she was a passenger or not, and hence if she was included in the total.
I would to normally do this, but I'll explain the incredibly simple logic just to be clear to anyone that is in some doubt somehow.
- If she is a passenger, there are 17 passengers INCLUDING Sophie, and 21 are added making 38 total passengers including Sophie, as she is a passenger.
- If she is not a passenger, there are 17 passengers NOT INCLUDING Sohpie, and 21 are added making 38 (plus Sophie who is not a passenger).
Either way the answer is 38.
Of course, what the pedantic 8 yo should have asked (and kudos for asking questions at all), is are all the "people" that got on "passengers". After all, if they are, then why not say "21 more passengers get on"? Why use a different word ("people") in that part of the question.
Yes, if Sophie is one of the 21, and not a passenger (e.g driver), then just like any other case where the 21 are not all passengers, it changes the answer - but that because the 21 are not all passengers rather than Sophie's status as such.