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Mr. Smith invests a certain amount of money at 8% and twice as much at 5%. If his annual income from the two investments is $720, how much does he have invested at 5%? (in $)

 Mar 10, 2020
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Let the amount of money Mr. Smith invested at \(8\)% be \(m\). This makes the amount of money Mr. Smith invested at \(5\)% equal to \(2m\).

 

Now we can create an equation:

 \($0.08m + 0.05 \cdot $2m = $720\)

 

Simplifying the equation: 

\(0.05 \cdot $2m = $0.1m\).

 

And the simplified equation: 
\($0.08m + $0.1m = $720\)

 

Adding like terms: 

\($0.18m = $720\)

 

Solving for \(m\):

\({0.18m \over 18} = {720 \over 18}\)

\(0.01m = $40\)

\(0.01m \cdot 100 = 40 \cdot 100\)

\(m = 4000\)

 

Mr. Smith invested \($4000\) at \(8\)%, so he invested \($8000\) at \(5\)%.

 

ANSWER: \($8000\).

 

I hope this is helpful,

Catarinasmiley

 Mar 10, 2020

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