Question

13. A man borrowed 9,000 to repay the amount with interest of 1,000 by monthly instalments
decreasing successively by < 20. In how many months was the loan repaid, if the first instalment
of 640 was paid one month after the sum was lent? solve


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Aph​

Answer 1

Answer:

The amount of money that man borrows is Rs8000 and the interest he has to pay is Rs1360.

The total money he has to pay is,

8000+1360=Rs9360

Since, he has to pay in 12 installments with a difference of 40 in each installment, then, it will form an A.P. where d=−40, n=12 and S

n

=9360.

Therefore,

S

n

=

2

n

[2a+(n−1)d]

9360=

2

12

[2a+(12−1)(−40)]

9360=6(2a−440)

1560=2a−440

2a=2000

a=1000

The last term in A.P. is,

a

n

=a+(n−1)d

=1000+(12−1)(−40)

=1000−440

=560

Therefore, the first installment is Rs1000 and the last installment is Rs560.

Step-by-step explanation:

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