Let's say that you are a baseball pitcher. And, let's say that your name is Tom Gordon. Now, let's say that it's the first game of the season, and you are brought into the game in the top of the 9th inning with the score tied 6-6. Then, let's say that you manage to get only one out, while giving up four hits, one walk and five earned runs.
Therefore, using the formula that is used to calculate a pitcher's earned run average (divide the total earned runs by the total innings pitched then multiply by nine - so that's 5 divided by 1/3 then multiplied by 9), you, Tom Gordon, have an E.R.A. of 135.00.
That's not good. Not good at all.