The difference between simple interest and compound interest of a certain sum of money at 40% per annum for 1 year is Rs.300. Then the sum is: (Interest being compound half yearly)

Rs.7500

Simple interest ⇒ 40% 

Compounded interest ⇒ 20% + 20% + \(\frac{20 × 20}{100}\)% ⇒ 44%

Diff. b/w C.I & S.I. for two years ⇒ 44% - 40% ⇒ 4%

ATQ,

4% of P = 300

100% of P = \(\frac{300}{4}\) × 100

Principal = Rs.7500