Question

Find the sum of first 24 terms of the AP whose nth term is 3 + 2n

• A. 624
• B. 756
• C. 672
• D. 840

Answer 1

Answer:

C. 672

$a_n=3+2n$

$a_1=3+2=5$

$a_2=3+4=7$

$d=7-5=2$

$S_n=n/2(2a+(n-1)d$

$S_{24}=24/2\times(2\times5+(24-1)2$

$=12(10+46)$

$=12\times56$

$=672$