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 30th installment? What amount of loan does he still have to pay after the 30th 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`