Question

if ajit saves rs.400 more each year than he did the year before and if he saves rs. 2000 in the first year, after how many years will his savings be more than rs.100000 altogether?​

Answer 1

Answer:

19 years

Step-by-step explanation:

The savings will be

2000, 2000+400, 2000+400+400,....

This series is in arithmetic progression.

where a=2000 and d=400

Let n= number of years to get the sum of savings as Rs.

Sn=n2(2a+(n−1)d)

100000=n2(2*2000+(n−1)400)

100000=n2(4000+400n−400)

100000=n2(3600+400n)

100000=n(1800+200n)

Dividing by 200

500=9n+n2

n2+9n−500=0

Solving this using quadratic formula ,

we get, n=18.3 years