Where Is the Fake Gold?

There are five bags of gold coins. One of the bags contains fake gold. See if you can figure out which bag it is.

 

Here's what you know:

• Each bag contains at least 10 gold coins.
  
  
• All the gold coins, real and fake, look identical.
  
  
• The real gold coins weigh 1.0 ounces.
  
  
• The fake gold coins weigh 1.1 ounces.
  
  
• You can't tell by picking up the bags or the coins which are heavier.
  
  
• To determine which bag has the fake gold coins, you can place any of the coins on a scale but you can only check the weight of the coins once.