A man save Rs. 400 more each years than he did the year before. If he saves Rs. 2000 in the first year after how mny years will his savings be more than Rs. 100000 altogether?

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 200500=9n+n2n2+9n-500=0Solving this using quadratic formula we getn=18.3 years.

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