Simple Interest on an Amount at 4% per Annum for 13 Months is More than the Simple Interest on the Same Sum for 8 Months at 6% per Annum by Rs. 40 What is the Principal Amount

Answer: Answer: Let the principle amount be ‘x’

Interest for 13 months at 4% p.a.- 

Interest for one month= 4/12 = 1/3%

So, Interest for 13 months= 1/3 x 13 = 13/3%

Interest for 8 months at 6% p.a.-

Interest for one month= 6/12 = ½%

So, interest for 8 months = ½ x 8 = 4% 

Given that, 13/3% of x  =  4% of x + 40 

13x/ 300 = 4x/100 + 40

13x/300 – 4x/100 = 40

1/300 (13x- 12x) = 40 [taking LCM]

 x = 40 x 300 = 12000.

Hence, the principal amount is Rs. 12000.