Question 77317
{{{880=800+(800)r(2)}}} plug in A=880, P=800, and t=2
{{{80=(800)r(2)}}} Subtract 800 from both sides
{{{80/800=r(2)}}} Divide both sides by 800
{{{(1/10)/2=r}}} Divide both sides by 2
{{{r=1/20}}}

So the interest rate (in decimal form) is:

0.05

which converts to a percentage by this procedure 

0.05*100=5

So the interest rate is 5%