A crew of spiders moved into the scary old house and started working at once. They spun 2 webs on the first night, and 7 webs on the second night. On the third night they wove 12 webs. Every night they made 5 more webs than they had made the night before. If the spiders kept spinning in this way, on what night did they spin their 60th web?
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1 answer
2 + 7 + 12 + 17 + 22 = 60