James wants to build a 16-foot by 20-foot quilt. He uses patches that are each 4 square feet. The first 10 patches cost $10 each and then each patch after that cost half as much. How much do the patches for the quilt cost?
Let's be accurate as possible. Think before you answer.
450
The patch is 16 * 20 = 320 square feet.

So he needs 320 / 4 = 80 patches.

The first 10 patches cost 10 * 10 = $100.

He gets a discount on the next 80 - 10 = 70 patches.

They each cost 10 / 2 = $5.

So in total they cost 70 * 5 = $350.

That means in total he paid 100 + 350 = $450.

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So, the final answer is 450