Tanvika purchases every year National Saving Certificates of value exceeding the last year purchases by Rs. 25. After 20 years, he find the total value of certificates purchased by him is Rs. 7250. Find the value of the certificates purchased.
(i) in the first year. (ii) in the 12th year.
Sequence of savings is 50, 100, 150,.........
Since, common difference between any two consecutive terms is constant (i.e., 50).
So, given sequence are in A .P.
Here, a = 50, d = 50, Sn = 10,500
Since, n = –21 is not possible.
Hence an = 20
i.e., In 20 months he will save Rs. 10500.