Dear XZY,

This question is related more to common sense than to maths, one of those quiz questions just to test your IQ.. but its a nice one.

The concept is that what the farmer has to pay, in addition to Rs 12,000, is the sum of interests paid by him in n months.

Now, in the first month, he pays 500 + interest on 5500

In second month, he pays 500 + interest on 5000

so on so on... till he pays

500 + interest on 500

and lastly, an installment of 500 with zero interest.

So the total interest paid by him is..

12% of ( 5500 + 5000 + 4500 + 4000 + 3500 + 3000 + ...... + 1000 + 500 )

= 12% of 500 ( 11 + 10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 )

= 12% of 500.(11.12/2)

=3960.

So the total cost of the tractor will be Rs. 15,960.

Tell me if it is not clear to u.