NCERT Class XI Mathematics - Sequences and Series - Solutions

Question : 106

Total: 106

Shamshad Ali buys a scooter for Rs 22000. He pays Rs 4000 cash and agrees to pay the balance in annual installment of Rs 1000 plus 10% interest on the unpaid amount. How much will the scooter cost him?

Solution:

Shamshad Ali buys a scooter for Rs. 22000. After paying Rs. 4000, Shamshad Ali left with Rs. 18000.
1st interest paid = Rs.

18000×10

100

= Rs. 1800
2nd interest paid = Rs.

17000×10

100

= Rs. 1700
..................
..........................
..........................
18th interest paid = Rs.

1000×10

100

= Rs. 100
Total amount of interest = Rs. [1800 + 1700 + ..... + 100]
= Rs.

[1800 + 100]
Since 1800, 1700 ..., 100 is an A.P. with n = 18, a = 1800, l = 100
= Rs. [9 × 1900] = Rs. 17100
∴ The cost of scooter = Rs. [22000 + 17100] = Rs. 39100.

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