Answer:
The interest rate is 8% simple interest.
Step-by-step explanation:
Let the investment of $555 is getting r% simple interest for 6 years to become the balance of $821.4.
So, from the equation of the simple interest we can write
[tex]821.4 = 555(1 + \frac{6r}{100})[/tex]
⇒ [tex](1 + \frac{6r}{100}) = 1.48[/tex]
⇒ [tex]\frac{6r}{100} = 0.48[/tex]
⇒ r = 8%
Therefore, the interest rate is 8% simple interest. ( Answer )
