Question

Find the sum of the first 15 terms of the series 3 + 5 + 7 + 9 +. . . . . . n terms.___

Answer 1

Given Series is an AP

Sum of n terms of an AP if first term = 3 and common difference = 2

$S_n$ = $\frac{n}{2}$ (2a + (n – 1)d)

$S_{20}$ = $\frac{15}{2}$( 6 + 14 $\times$ 2) = 255