The entities in the centre of your Venn diagram are in all 3 groups - so each one has been counted 3 times.jsl wrote:Great solution... however, the above has been driving me crazy for ages... How did you calculate 6? I understand that there were 3 students so in my venn diagram, I have 3 in the centre. However, where does the other 3 come from? I noticed this was one of the trap answers too!xilef wrote:3 students take 3 classes that means you have 6 duplicate entries
If someone could explain, I'd be really thankful.
Jon
Since we only want to count each one once, we need to subtract 2 of the 3 times that we've counted them so far. Therefore, we subtract double the number of entities in the centre.
