Question
Carl folded 21 paper swans on the first day. Each day he did 10 more paper swans than the previous day. On the last day, he made 171 swans. How many days did he fold paper swans?
2 m

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Carl folded 21 paper swans on the first day. Each day he did 10 more paper swans than the previous day. On the last day, he made 171 swans. How many days did he fold paper swans?