A radio sold a loss of 2.5%. Had he sold it for Tk. 100 more, he would have gained 7.5%. In order to gain 12.5%, he should sell it for:

Cost Price = 100
Selling price = 100 - 2.5 = 97.5
New selling price at 7.5% = 107.5
difference between two selling price = 107.5 - 97.5 = 10
10% price is equal to Tk. 100
1% price is equal to Tk. 100/10%
100% price is equal to Tk. (100/10%) × 100
= 1000
so Cost price = 1000
SP at 12.5% = (100+12.5/100) × 1000
= 1125