1. Mary got a job with a starting salary of Rs. 15000/- per month. She will get an incentive of Rs. 100/- per month. What will be her salary after 20 months?
Sol. Since Mary’s salary increases by Rs. 100 every month the successive salaries are in A.P.
Starting salary of Marry (a) = Rs. 15000
Monthly incentive in salary (d) = 100
No. of months (n) = 20
Salary after twenty months = t20 = ?
tn = a + (n – 1) d
∴ t20 = a + (20 – 1) d
∴ t20 = 15000 + 19 (100)
∴ t20 = 15000 + 1900
∴ t20 = 16900
