**Source:**Mind Your Decisions Blog

**Related Problem:**Expected Length of Last Straw - Breaking the back of a Camel - CSE Blog

**Problem:**

**Your boss tells you to bring him a cup of coffee from the company vending machine. The problem is the machine is broken. When you press the button for a drink, it will randomly fill a percentage of the cup (between 0 and 100 percent). You know you need to bring a full cup back to your boss.**

What’s the expected number of times you will have to fill the cup?

**Example:**The machine fills the cup 10 percent, then 30 percent, then 80 percent–>the cup is full plus 20 percent that you throw away or drink yourself. It took 3 fills of the cup.