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In an arithmetic sequence with 25 terms, if the first term is 60 and last term i...


Question

In an arithmetic sequence with 25 terms, if the first term is 60 and last term is -12, the sum of the terms of the sequence is

Options

A) 600

B) 2400

C) 900

D) 1800

The correct answer is A.

Explanation:

\(-12=60 + (25-1)d\)
\(24d= -72\)
\(d=-3\)

\(s=\cfrac{n}{2}(2a + (n-1)d)\)
\(\cfrac{25}{2}(2 \times 60 + (25-1)-3)\)
\(\cfrac{25}{2}(120-72)\)
\(\cfrac{25}{2}(48)\)
\(=600\)

Explanation provided by Uwakwe Chukwuemeka


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