Answer :

To find the principal that will earn $55.99 interest at an annual interest rate of 9.75% from February 4, 2017, to July 6, 2017, we need to follow these steps:

1. Calculate the number of days between the two dates.

- Days in February after the 4th: \( 28 - 4 = 24 \)
- Days in March: 31
- Days in April: 30
- Days in May: 31
- Days in June: 30
- Days in July until the 6th: 6

Adding these up gives:
[tex]\[ 24 + 31 + 30 + 31 + 30 + 6 = 152 \text{ days} \][/tex]

2. Convert the number of days to a fraction of a year.

Since there are 365 days in a year:
[tex]\[ \text{Fraction of the year} = \frac{152}{365} \][/tex]

3. Set up the interest formula:

The formula for simple interest is:
[tex]\[ I = P \times r \times t \][/tex]
Where:
- \( I \) is the interest earned ($55.99)
- \( P \) is the principal (the amount we need to find)
- \( r \) is the annual interest rate (9.75% or 0.0975 as a decimal)
- \( t \) is the time in years (fraction of the year we calculated)

4. Substitute the known values into the formula and solve for \( P \):

Substitute \( I = 55.99 \), \( r = 0.0975 \), and \( t = \frac{152}{365} \):
[tex]\[ 55.99 = P \times 0.0975 \times \frac{152}{365} \][/tex]

5. Simplify the equation to isolate \( P \):

First, calculate \( t = \frac{152}{365} \):
[tex]\[ t \approx 0.4164 \][/tex]

Then,
[tex]\[ 55.99 = P \times 0.0975 \times 0.4164 \][/tex]
[tex]\[ 55.99 = P \times 0.04057 \][/tex]

Finally, divide both sides by 0.04057 to solve for \( P \):
[tex]\[ P = \frac{55.99}{0.04057} \][/tex]

6. Calculate the principal:
[tex]\[ P \approx \frac{55.99}{0.04057} \approx 1379.93 \][/tex]

So, the principal that will earn [tex]$55.99 in interest at an annual interest rate of 9.75% from February 4, 2017, to July 6, 2017, is approximately $[/tex]1379.93.

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