There are 49 heads and 100 feet in the same cage? (solved by equation)
Suppose there are x chickens, then there are 49-x rabbits
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- 18. It is known that it is the sum of the first n terms of Sn arithmetic sequence, and the equal proportion middle term of one third S3 and one fourth S4 is one fifth S5 And the mean term of one third S3 and one fourth S4 is 1
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