How do I work this out ?

Question

Please explain how I work out this problem and what is the formula?:

Merchant banks offer simple interest on all investments. Merchant bank A had an investor invest $10000 for 5 years. Merchant bank B had a different investor invested $15000 for 3 years. Investor B obtained $2500 more in interest than investor A because the rate of interest per annum she received was 6% greater than the interest obtained by investor A. Find the simple interest and rate of interest for each investor


Thank you

Answer 1

A:

i = 10000(r)(5)

B:

i = 15000(r + 0.06)(3)

 

B = A + 2500

15000(r + 0.06)(3) = 10000(r)(5) + 2500

45000(r + 0.06) = 50000r + 2500

45000r + 2700 = 50000r + 2500

2700 = 5000r + 2500

200 = 5000r

0.04 = r