Question

on 1st jan 2016 sanika decided to save rupees 10 rupees 11 on second day, rupees 12 on third day if she decided to save like this then on 31st December 2016 what would be her total savings ​

Answer 1

2016 is leap year.

Therefore, Number of days from 1st January 2016 to 31st December 2016 = 366

The saving of Sanika per day, with beginning of first day saving is 10, 11 , 12 ••••••366

The first day saving is (a) = 10

Difference is saving made in two successive days ( d) = 1

Total number of days in year 2016 (n) = 366

$\sf \: By Formula,$

$\sf \: S_{n} = \dfrac{n}{2} [2a + (n-1) d]$

$\sf \: S_{366} =\dfrac{366}{2}[2×10+(366-1)1]$

$\sf \: = 183 [20 + 365]$

$\sf \: = 183 × 385$

$\sf \green{\therefore \: S_{366} = 70,455}$

Therefore, Sanika saves ₹70,455 in year 2016.