Question 14 Marks
A farmer borrows ₹ 1,000 and agrees to repay with a total interest of ₹ 140, in 12 instalments. Each instalment being less than the preceding instalment by ₹ 10. What should be the amount of his first and last instalment?
Answer
View full question & answer→Total Sum $S_n = 1000 + 140 = 1140$. $n=12, d=-10$.
$S_n = \frac{n}{2}[2a + (n-1)d]$
$1140 = 6[2a + 11(-10)] \implies 190 = 2a - 110 \implies 2a = 300 \implies a = 150$.
First instalment = 150. Last (12th) = $150 + 11(-10) = 40$.
$S_n = \frac{n}{2}[2a + (n-1)d]$
$1140 = 6[2a + 11(-10)] \implies 190 = 2a - 110 \implies 2a = 300 \implies a = 150$.
First instalment = 150. Last (12th) = $150 + 11(-10) = 40$.