Question

Babubhai borrows Rs. $4000$ and agrees to repay with a total interest of Rs. $500$ in $10$ installations, each instalment being less than the preceding instalment by Rs. $10$. What should be the first and last installment?

Answer 1

The installments are in A.P. with difference 10.

Hence,

$a+a-10+a-20+a-30+.....+a-90=500$

$\frac{10(a+a-90)}{2}=500$

$2a-90=100$

$a=95$