Final answer:
To figure out how long it will take for Sally's $1,300 to double with a 2% simple interest rate, we set the interest equal to the principal and solve for time. According to the simple interest formula, it will take Sally 50 years for her money to double.
Step-by-step explanation:
To determine how long Sally needs to wait before her money doubled using simple interest, we can use the formula for simple interest, which is I = P * r * t, where I stands for interest, P is the principal amount, r is the rate of interest, and t is the time in years.
In this scenario, Sally's money will double when the interest earned equals the principal amount. Therefore, Sally's initial deposit, or principal (P), is $1,300. The interest rate (r) is 2%, or 0.02 as a decimal. To double her money, the interest (I) must be $1,300 as well.
Substituting the known variables into the formula gives us:
1300 = 1300 * 0.02 * t
Solving for t gives:
t = 1300 / (1300 * 0.02)
t = 50 years
Therefore, Sally will need to wait 50 years before her money is doubled at a 2% simple interest rate.