NCERT Class XI Mathematics - Sequences and Series - Solutions
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Question : 105
Total: 106
A farmer buys a used tractor for Rs. 12000. He pays Rs 6000 cash and agrees to pay the balance in annual installments of Rs. 500 plus 12% interest on the unpaid amount. How much will the tractor cost him?
Solution:
Farmer purchased a tractor for Rs. 12,000. After paying Rs. 6000, he will left with Rs. 6000.
1st interest paid = Rs.
2nd interest paid = Rs.
...................
...........................
..........................
12th interest paid = Rs.
Total amount of interest = Rs. [720 + 660 + ..... + 60]
= Rs.[
( 720 + 60 ) ]
Since 720, 660, ...., 60 is an A.P. with n = 12, a = 720, l = 60
= Rs. (6 × 780) = Rs. 4680
∴ The cost of tractor = Rs. (12000 + 4680) = Rs. 16680.
1st interest paid = Rs.
2nd interest paid = Rs.
...................
...........................
..........................
12th interest paid = Rs.
Total amount of interest = Rs. [720 + 660 + ..... + 60]
= Rs.
Since 720, 660, ...., 60 is an A.P. with n = 12, a = 720, l = 60
= Rs. (6 × 780) = Rs. 4680
∴ The cost of tractor = Rs. (12000 + 4680) = Rs. 16680.
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