AMC 10 Daily Practice - Sequences

Complete problem set with solutions and individual problem pages

Problem 1 Easy

S_{n} is the sum of the first n terms of the arithmetic sequence \left\{a_{n}\right\}. If d=2 and S_{5}=15, then a_{1}=            .

  • A.

    -1

  • B.

    -2

  • C.

    -3

  • D.

    -4

Answer:A

S_{5}=5a_{1}+\frac{5\times 4}{2}\times 2=15,

then a_{1}=-1.

Related Problems
Problem 2 AMC 10 Daily Practice - Sequences
Problem 3 AMC 10 Daily Practice - Sequences
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