Using the formula for the simple interest, we have:
S = P(R)(T) ( S: simple interest, P: principal, R: interest rate, T: time)
900 = 900(R)(2) (Replacing the values)
1 = (R)(2) (Dividing by 900 on both sides of the equation)
0.5 = R (Dividing on both sides of the equation by 2)
0.5 is equivalent to 50%
The answer is 50%.