This brain teaser sounds like a simple subtraction and addition problem, but there’s a small detail that is easy to miss.
You are in a room with 70 people.
That means there are actually 71 people in the room when you include yourself.
Then 30 people leave:
71 − 30 = 41
Next, 15 people return:
41 + 15 = 56
The trick is remembering that you were in the room too.
Answer: 56 people.


