Peter invested a certain sum of money in a simple interest bond whose value grew to $300 at the end of 3 years and further to $400 at the end of another 5 years. What was the rate of interest in which he invested his sum?
Choose the correct choice from the following answers
A) 12 %  B) 12.5 %  C) 6.67 %  D) 6.25 %  E) 8.33 %

Rationale: answer initial amount invested = $ x amount at the end of year 3 = $ 300 amount at the end of year 8 ( another 5 years ) = $ 400 therefore , the interest earned for the 5 year period between the 3 rd year and 8 th year = $ 400 - $ 300 = $ 100 as the simple interest earned for a period of 5 years is $ 100 , interest earned per year = $ 20 . therefore , interest earned for 3 years = 3 * 20 = $ 60 . hence , initial amount invested x = amount after 3 years - interest for 3 years = 300 - 60 = $ 240 . rate of interest = ( interest per year / principal ) * 100 = 20 / 240 * 100 = 8.33 % choice is ( e )
Answer: E