Marla invested $78,170 in a simple interest account. after 9 years and no additional deposits or withdrawals, the account balance was $150,606.59. find the interest rate for the account.

The interest rate for the account is

Step-by-step explanation:

we know that

The simple interest formula is equal to

where

A is the Final Investment Value

P is the Principal amount of money to be invested

r is the rate of interest  

t is Number of Time Periods

in this problem we have

substitute in the formula above  and solve for r

convert to percentage

then