Jaspal Singh repays his total loan of `Rs.` `118000` by paying every month starting with the first installment of `Rs.` `1000`. If he increases the installment by `Rs.` `100` every month, what amount will be paid by him in the `30`th installment? What amount of loan does he still have to pay after the `30`th installment?

Explanation

Here, a=Rs. 1000, d=Rs. 100
`:. a_(30)=a+29d`
`=Rs. (1000+29xx100)=Rs. 3,900`
`rArr` Amount paid in 30th instalment = Rs. 3,900
and `S_(30)=Rs. (30)/(2)(2a+29)`
`=Rs. 15(2000+29xx100)=Rs. 15xx 4900=Rs. 73,500`
`rArr` Amount still have to pay after 30th instalment
`=Rs. 1,18,000-Rs. 73,500=Rs. 45,500`