Indian Institute of Foreign Trade 2015 Solved Paper

Question : 15 of 124

Marks: +1, -0

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:

6 months
12 months
18 months
24 months

Validate

Solution:

(c) Salary of Seema = ₹3000
Savings for 1st three months = 900
Saving for next months = 350, 400, 450....
Now, 900 + 350 + 400 + 450 + ....n terms = 11400
350 + 400 + 450 + ..... + upto n terms = 10500
It is an A.P where a = 350 and d = 50

{ n }/ { 2 } [ 2 × 350 + ( n - 1 ) 50 ] = 10500

n [ 650 + 50 n ] = 21000

50 n ^ { 2 } + 650 n - 21000 = 0

n ^ { 2 } + 13 n - 420 = 0

n ^ { 2 } - 28 n - 15 n - 420 = 0

( n + 28 ) ( n - 15 ) = 0

n = 15

as n can't be negative
So total months = 15 + 3 = 18

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