Seema has joined a new Company after the completion of her B.Tech from a reputed engineering college in Chennai. She saves 10% of her income in each of the first three months of her service and for every subsequent month, her savings are Rs. 50 more than the savings of the immediate previous month. If her joining income was Rs. 3000, her total savings from the start of the service will be Rs.11400 in:
Explanation:
Seema saves Rs. 900 in first three months.
Let she reach the given amount in X more months.
She would save 300X + 50 + 50 × 2 + 50 × 3 +......... + 50 × X = 11400 − 900
∴ 300X + 50(1 + 2 + 3 +......+ X) = 10500
∴ X2 + 13X - 420 = 0
On solving, we get X = 15.
Thus, in 15 + 3 = 18 months her savings will be Rs. 11,400.
Hence, option (c).