Indian Institute of Foreign Trade 2009 Solved Paper

first month he will have deficiency of 2000, second month he will have deficiency of 2500, Third month he will have deficiency of 3000, and so on
He won't borrow until all of his savings (60000) gets exhausted i.e. until 60000 - (2000 + 2500 + 3000 + ........ up tonth month ) becomes negative
i.e 60000<

n

2

×(4000+(n−1)500)
i.e 1200<n×(35+5n)
i.e 240<n×(7+n)
This condition first becomes true for n=13 therefore Rashid will have to borrow from 13th month
Therefor the answer is option 'D'