Question

On 1st January 2016, sanika decides to save 10Rs, 11Rs on second day, 12Rs on third day if she decides to save like this, then on 31st December 2016, what would be her total saving

Answer 1

a=10
d=11-10=1
n=365
Sn=
$\frac{n}{2} |2a + (n - 1)d|$
$\frac{365}{2 | } |2 \times 10 + (365 - 1)1|$
$\frac{365}{2 } |20 + 364|$
$\frac{365}{2} \times 384$
=365×192
=70080