Answer :

**Given:** S_{n} = Rs 118000

a = Rs 1000

d = Rs 100

**To find:** S_{30}

Loan after 30^{th} installment

**Formula Used:**

Sum of “n” terms of an AP:

Where S_{n} is the sum of first n terms

n = no of terms

a = first term

d = common difference

**Explanation:**

Given that,

Jaspal singh takes total loan, S_{n} = Rs 118000

He repays his total loan by paying every month.

His first installment, a = Rs 1000

Second installment = 1000 + 100 = 1100

Third installment = 1100 + 100 = 1200 and so on

Thus, we have 1000, 1100, 1200, … which form an AP, with

first term, a = 1000

common difference, d = 1100 – 1000 = 100

nth term of an AP

So, amount paid in 30 installments = sum of first 30 terms of this AP

= 15(2000 + 2900)

= 15(4900) = 73500

So, he pays Rs 73500 in 30 installments

Loan left = total loan - paid lone

= 118000 - 73500 = 44500 Rs

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