Question

Find the sum of $60$ terms of A.P $3,5,7,...$

Answer 1

$a=3,d=5-3=2$

$S_n=\frac{n}{2}[2a+(n-1)d]$

$S_{60}=\frac{60}{2}[2\times 3+(60-1)\times 2]$

$S_{60}=30[6+\left(59\right)\times 2]$

$S_{60}=30\times [6+118]$

$S_{60}=30\times 124=3720$

$\therefore {60}^{th}$ term of the A.P is $3720$