Question 147632
 given P= $ 1420
       I= $306.72
       t = 3yrs

  simple interest , I = pnr/100 , Where n, no of yrs & r is rate of interest.

          we have to find interest rate , r.

                 r= I*100 / pn
             
                r  = (306.72 * 100 )/1420* 3=  30672/4260 = 7.2

     Interest rate  = 7.2%