Question 87173
Use the simple interest formula:


{{{I=Prt}}}



{{{306.72=(1420)r(3)}}} Plug in P=1420, I=306.72, and t=3 



{{{306.72=4260r}}} Multiply


{{{306.72/4260=r}}} Divide both sides by 4260


{{{0.072=r}}}


Now multiply the figure by 100 to get a percentage:


{{{100*0.072=7.2}}}


So the interest rate is 7.2%