Okay hear this someone came into my shop and stole 100 from

Okay hear this. ... someone came into my shop and stole $100 from the register without my knowledge. The person came back with the same $100 five minutes later and he bought $70 in items and gave him back $30 change. How much money did I loose?

Solution

Here in First case clearly we can say you lost $100.

After 5 min the person came to your shop and purchased items worth $70 and and you given back the change remaining $30 for the same $100.

So you got your $100 back but again you lost $100 in terms of $70 items and $30 change.

That means the thief took the items and change without any money.

So finally you have lost of $100.