Half a bus in the real world

We have been working on story problems for a month.
We have been using combine and compare schemas and there seems to be some improvement with basic questions.

So today there was a trick question.

5 classes are going on a field trip. Each class has 23 students. 2 adults will go with each class.
The buses hold 40 people. How many buses will be needed?

4/5 kids gave the answer as 3 and 5 left over. One student said the answer was 3.12 buses.


There are a lot of numbers in this problem. Small numbers but lots of them.
Students had a hard time telling about the relationships between the numbers.


To think about.
How do you get students to see the relationships between numbers in a problem.... and to decide which numbers go with which?