# NCERT Class 11 Mathematics Solutions: Chapter 9 –Sequences and Series Miscellaneous Exercise 9 Part 15

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1. A farmer buys a used tractor for . He pays cash and agrees to pay the balance in annual installments of plus interest on the unpaid amount. How much will be the tractor cost him?

Answer:

It is given that the farmer pays in cash.

So, unpaid amount

According to the given condition, the interest paid annually is

So, total interest to be paid

Now, the series is an A.P. with both the first term and common difference equal to .

Consider the number of terms of the A.P. be .

Sum of the A.P.

So, total interest to be paid

Cost of tractor

2. Shamshad Ali buys a scooter for . He pays cash and agrees to pay the balance in annual installment of plus interest on the unpaid amount. How much will the scooter cost him?

Answer:

It is given that Shamshad Ali buys a scooter for and pays in cash.

Unpaid amount

According to the given condition, the interest paid annually is

Total interest to be paid

Here, forms an A.P. with first term and common difference both equal to .

Consider the number of terms be .

Total interest paid

Cost of scooter