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, 2004

Algebra Difficulty 2.0 Junior Prove it Canada

In an arithmetic sequence with five terms, the sum of the first two terms is $2$ and the sum of the last two terms is $-18$ . What is the third term of this sequence? (An arithmetic sequence is a sequence in which each term after the first is obtained from the previous term by adding a constant. For example, $3, 5, 7, 9, 11$ is an arithmetic sequence with five terms.)

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.