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3 years ago

Serena invests $2500 for 3 years and 6 months and earns $328.13. What was the rate of interest? Explain how you solved.

Mathematics

1 answer:

NARA [144]3 years ago

6 0

Answer:

4.38%

Step-by-step explanation:

Assuming simple interest, we start by writing the formula for simple interest.

$SI=Prt$

Where

SI is the interest amount (328.13)

P is the principal amount (2500)

r is the rate of interest (what we need to find)

t is the time, in years (t = 3)

Since we want rate of interest, we re-arrange the formula to get r in terms of the other variables. Shown below:

$SI=Prt\\r=\frac{SI}{Pt}$

Now we simply plug-in the information we know and find r:

$r=\frac{328.13}{(2500)(3)}\\r=0.0438$

To convert into percentage, we multiply by 100:

r = 0.0438 * 100 = 4.38%

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Step-by-step explanation:

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3. To find the y-coordinate of the vertex you use the parabola equation and x-coordinate of the vertex ( $f(-\frac{b}{2a})=a(-\frac{b}{2a})^2+b(-\frac{b}{2a})+c$ )

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$\mathrm{Add\:}8\mathrm{\:to\:both\:sides}$

$x^2-6x-8+8=0+8$

$\mathrm{Simplify}$

$4x^2-6x=8$

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$\left(x-\frac{3}{4}\right)^2=\frac{41}{16}$

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