If Matt buys 10 key chains for $20, then the price per key chain is $20/10 = $2.
If Matt buys 4 key chains for $12, then the price per key chain is $12/4 = $3.
By choosing to buy in packs of 10, Matt can save $3 - $2 = $1 per key chain.
If Matt buys 20 key chains, he can save $1 x 20 = $20 in total.
#### 20
The answer is: 20
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If Matt chooses to buy 20 key chains at a lower price, either in packs of 10 for $20 or in packs of 4 for $12, how much money can he save?

### Answer:
