Question

A man starts repaying a loan as first instalment of Rs. 100. If he increases the instalment by Rs. 5 every month, what amount he will pay in the ${30}^{th}$ instalment ?

Answer 1

Amount of $1^{st}$ instalment = Rs. 100

Amount of $2^{nd}$ instalment = Rs. 105

Sequence of amount is 100, 105, ....

Here a = 100, d = 105 - 100 = 5

and n = 30

We know that $a_n=a+(n-1)$

$\therefore d_{30}=100+(30-1)\times 5$

$\Rightarrow a_{30}=100+29\times 5$

$\Rightarrow a_{30}100+145=Rs.245$

Thus, the amount of ${30}^{th}$ instalment is Rs. 245.