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Consider the AP 5, 8, 11, 14, ... What do its first 15 terms add up to?

Class 10Sum of n Terms of an APAlgebra — Sequences

A390
B375
C405
D360

Step-by-Step Solution

a = 5, d = 3, n = 15. S = \frac{15}{2}

[2(5) + 14(3)] =

\frac{15}{2}

[10 + 42] =

\frac{15}{2}

(52) = 15 (26) = 390

.

Answer: A) 390

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