IIT JEE , AIEEE Forum - Mathematics , Algebra

freestyler_fx

a farmer buys a tractor for 12000.pays 6000 cash and agrees to pay balance i n monthly installments of rs 500+12%interest on unpaid amount..how much will the tractor cost him???

edison

Total cost of tractor will be as follows

6000 + (500 + 6000x12/100 x 1/12) + (500 + 5500x12/100 x 1/12) +

.....(500 + 500x12/100 x 1/12)

= 12000 + (1/100) x (6000 + 5500 +5000 +...+500)

= 12000 + 5 x (12 + 11 +10 + 9 + ... +1)

= 12000 + 5 x 12x 13/2

= 12000 + 30 x 13

= 12000 + 390 = 12390 ans

sudeep.kumar

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.

sudeep.kumar

Is it 12% per annum or per month... if its per annum.... edison is correct.. or else i m.. but both the approaches are same.

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