The Simple Interest on some amount of money for 2 years is Rs.400. If 'r' is 4% more, then the Simple Interest will be Rs.400 more. What is the original amount of money?

Correct option is D

Given:
The simple interest on some amount of money for 2 years is Rs.400.
If 'r' is 4% more, then the Simple Interest will be Rs.400 more.
Formula used:
Simple interest = (Principal × rate × time)/100
Solution:
SI = Rs. 400, rate = r% and time = 2 year
 As we know,
SI = Prt/100
=> 400 = (P × r × 2)/100
Pr = 20,000 --- (1)
Again,
Rate = (r + 4) %,
SI = 400 + 400 = Rs. 800
Time = 2 years
SI = Prt/100
800 = [P (r + 4) × 2]/100
Pr + 4P = 800 × 50
From equation (1)
=> 20,000 + 4P = 40,000
=> 4P = 40,000 – 20,000 = 20,000
=> p = 20,000/4
=> p = 5,000