jcdavi34
Macy currently has a balance of $3,418.82 in an account earning simple interest. Eighteen years ago she opened the account with an initial deposit of $2,481. What is the interest rate on the account?
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jcdavi34
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is anyone there any members can help me please
jdoe0001
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do you happen to have the Interest Rate Formula?
jcdavi34
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no :(
jdoe0001
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or, I should say, if you stick "X" amount in the bank today, and they say they'll give you 5percent interest, how much would you expect in 1year?
jdoe0001
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would you expect X+[5percent of X]? after 1 year?
jdoe0001
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ok, what's 10% of 100? :)
jcdavi34
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10
jdoe0001
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ok, so if you put $100 in the bank, and they they'd give you 10 yearly interest, after 1 year, you'd expect $100+[10% of $100 = $10], thus $110 :)
jdoe0001
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Macy originally put $2481, after 18 years, with yearly interest, it became $3,418.82
so
$3,418.82 = $2481 + [$2481 * RATE] *18years
jcdavi34
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it ask for the interest rate
jcdavi34
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7.7%
1.5%
5.6%
2.1%
Numb3r1
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Even if it's earning simple interest, the interest will compound annually.
jdoe0001
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$$
A= 3,418.82\\
P= 2,481\\
r = ?
-------------\\
A=P+ Prt \implies P(1+rt)\\
A-P=Prt\implies \color{blue}{\cfrac{A-P}{Pt}=r}
$$
jdoe0001
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woops, ahemm
jcdavi34
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7.7%
1.5%
5.6%
2.1%
these are the answrs
jdoe0001
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$$
A= 3,418.82\\
P= 2,481\\
\color{blue}{r = ?}\\
-------------\\
A=P+ Prt \implies P(1+rt)\\
A-P=Prt\implies \color{blue}{\cfrac{A-P}{Pt}=r}
$$
jdoe0001
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@jcdavi34 what does that give you?
jdoe0001
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ohh,and T=18, 18years :/
jcdavi34
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i got 2.1%
jdoe0001
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$$
A= 3,418.82\\
P= 2,481\\
t=18\\
\color{blue}{r = ?}\\
-------------\\
A=P+ Prt \implies P(1+rt)\\
A-P=Prt\implies \color{blue}{\cfrac{A-P}{Pt}=r}
$$
what do you get?
jdoe0001
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2.1% that is :)
jcdavi34
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thanks!