Shamshad Ali buys a scooter for Rs. 2200. He pays Rs. 4000 cash and agrees to pay the balance in annual instalments of Rs. 1000 plus 10% interest on the unpaid amount. How much the scooter will cost him?

Explanation

`rs 2200 -> ` cost

`1yr -> 1000 + 10/100 xx 18000 = 1000 + 1800`

`2 yr-> 1000 + 10/100 xx 17000 = 1000 + 1700`

`n yr -> 1000 + 10/100 (18000 - (n-1)1000)`

`= 1000+ 1800 + 100 - n100`

`= 2700 - n(100)`

`S_n = [ sum 2900 - n(100)] + 4000`

`= 2900n - 100(n(n+1))/2 + 4000`

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