The cost of each key chain in packs of 10 for $20 is $20/10=$<<20/10=2>>2.

The cost of each key chain in packs of 4 for $12 is $12/4=$<<12/4=3>>3.

There is a price difference of $3-$2=$<<3-2=1>>1 per key chain between the two choices.

By buying 20 key chains at a lower price, Matt can save 20x$1=$<<20*1=20>>20.

# Answer

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<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Matt can buy key chains in packs of 10 for $20 or in packs of 4 for $12. How much money can he save if he chooses to buy 20 key chains at a lower price?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
20
Matt can buy key chains in packs of 10 for $20 or in packs of 4 for $12. How much money can he save if he chooses to buy 20 key chains at a lower price?
train