Answer:
$2000 was invested at 5% and $5000 was invested at 8%.
Step-by-step explanation:
Assuming the interest is simple interest.
Simple Interest Formula
I = Prt
where:
- I = interest earned.
- P = principal invested.
- r = interest rate (in decimal form).
- t = time (in years).
Given:
- Total P = $7000
- P₁ = principal invested at 5%
- P₂ = principal invested at 8%
- Total interest = $500
- r₁ = 5% = 0.05
- r₂ = 8% = 0.08
- t = 1 year
Create two equations from the given information:
[tex]\textsf{Equation 1}: \quad \sf P_1+P_2=7000[/tex]
[tex]\textsf{Equation 2}: \quad \sf P_1r_1t+P_2r_2t=I\implies 0.05P_1+0.08P_2=500[/tex]
Rewrite Equation 1 to make P₁ the subject:
[tex]\implies \sf P_1=7000-P_2[/tex]
Substitute this into Equation 2 and solve for P₂:
[tex]\implies \sf 0.05(7000-P_2)+0.08P_2=500[/tex]
[tex]\implies \sf 350-0.05P_2+0.08P_2=500[/tex]
[tex]\implies \sf 0.03P_2=150[/tex]
[tex]\implies \sf P_2=\dfrac{150}{0.03}[/tex]
[tex]\implies \sf P_2=5000[/tex]
Substitute the found value of P₂ into Equation 1 and solve for P₁:
[tex]\implies \sf P_1+5000=7000[/tex]
[tex]\implies \sf P_1=7000-5000[/tex]
[tex]\implies \sf P_1 = 2000[/tex]
$2000 was invested at 5% and $5000 was invested at 8%.
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