The cost of the planks for one birdhouse is 7 * 3 = $<<7*3=21>>21.

And the nails are a cost of 20 * 0.05 = $<<20*0.05=1>>1 for each birdhouse.

So to build one birdhouse one will need 21 + 1 = $<<21+1=22>>22.

So the cost of building 4 birdhouses is at 4 * 22 = $<<4*22=88>>88.

# Answer

88
Question:
Building one birdhouse requires 7 planks and 20 nails.  If 1 nail costs $0.05, and one plank costs $3, what is the cost, in dollars, to build 4 birdhouses?
Answer:
Let's think step by step.

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88
Building one birdhouse requires 7 planks and 20 nails.  If 1 nail costs $0.05, and one plank costs $3, what is the cost, in dollars, to build 4 birdhouses?
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