1. After investing for 3 years at 7% interest, your $400 investment will have grown to $490.02
2. After investing for 4 years at 5.60% interest, your $1,200 investment will have grown to $1,492
3. Solving our equation:
r = (1/18)((218/200) - 1) = 0.005
r = 0.005
Converting r decimal to R a percentage
R = 0.005 * 100 = 0.5%/month
Calculating the annual rate
0.5%/month × 12 months/year = 6%/year.
The interest rate required to get a total amount, principal plus interest, of $218.00 from simple interest on a principal of $200.00 over 1.5 years (18 months) is 0.5% per month.
4. Solving our equation:
r = (1/5)((1310/1000) - 1) = 0.062
r = 0.062
Converting r decimal to R a percentage
R = 0.062 * 100 = 6.2%/year
The interest rate required to get a total amount, principal plus interest, of $1,310.00 from simple interest on a principal of $1,000.00 over 5 years is 6.2% per year.
5. Calculation:
First, converting R percent to r a decimal
r = R/100 = 4%/100 = 0.04 per year,
then, solving our equation
t = (1/0.04)((810/750) - 1) = 2
t = 2 years
The time required to get a total amount, principal plus interest, of $810.00 from simple interest on a principal of $750.00 at an interest rate of 4% per year is 2 years.
6. First, converting R percent to r a decimal
r = R/100 = 5.5%/100 = 0.055 per year,
then, solving our equation
t = (1/0.055)((3325/2500) - 1) = 6
t = 6 years
The time required to get a total amount, principal plus interest, of $3,325.00 from simple interest on a principal of $2,500.00 at an interest rate of 5.5% per year is 6 years.
7. Solving our equation:
r = (1/6)((515.75/500) - 1) = 0.00525
r = 0.00525
Converting r decimal to R a percentage
R = 0.00525 * 100 = 0.525%/month
Calculating the annual rate
0.525%/month × 12 months/year = 6.3%/year.
The interest rate required to get a total amount, principal plus interest, of $515.75 from simple interest on a principal of $500.00 over 0.5 years (6 months) is 0.525% per month.
