Final answer:
Carmen should choose an interest rate of approximately 0.95238%.
Step-by-step explanation:
To find the rate of interest, we can use the formula for simple interest:
Interest = Principal x Rate x Time
Given that Carmen wants to invest $700 for 90 days and earn $63 in interest, we can substitute these values into the formula:
$63 = $700 x Rate x 90 days
To solve for the rate, we divide both sides of the equation by ($700 x 90):
Rate = $63 / ($700 x 90)
Calculating this, we find that the rate of interest Carmen should choose is approximately 0.0095238 or 0.95238%.