It is your birthday and you want to buy a bottle of perfume for ` 97.
![](http://www.hindu.com/mp/2004/07/21/images/2004072100810101.jpg)
Since you don't have cash you borrow ` 50 from your dad and ` 50 from your mom.
Now you have ` 100.
You purchase the perfume for ` 97.
You are left with ` 3 change.
You return ` 1 to your dad and ` 1 to your mom.
You keep the balance ` 1 for yourself.
After returning ` 1 each, you owe your mom ` 49 and your dad ` 49.
Added together ` 49 + ` 49 = ` 98 plus your ` 1 = ` 99.
Now, where is the missing ` 1 ???