A man accepts a position with an initial salary of Rs. 5200 per month. It is understood that the will receive an automatic increase of Rs. 320 in the very next month and each month thereafter. Find his salary for the tenth month What is his total earnings during the first year?

Explanation

Since the man get a fixed increment of Rs. 320 each month .
therefore this formsterm =5200 and common difference (d) =320
(i) salary for tenth month i.e., for n=10,
`a_(10)=a+(n-1)d`
`implies a_(10)=5200+(10-1)xx320`
`implies a_(10)=5200+9xx320`
`therefore a_(10) =5200+2880`
` therefore a_(10)=8080`
(ii) total earning during the first year .
in a year there are 12 month i.e., n=12,
`S_(12)=(12)/(2)[2xx5200+(12-1)320]`
`=6[10400+11xx320]`
`=6(10400+3520]=6xx13920=83520`