Amanda

Amanda borrowed $5000 from two sources: her parents and a credit union. Her parents charged 3% simple interest, and the credit union charged 6% simple interest. After one year, Amanda paid $225 in interest. Thus, Amanda borrowed $5000 from both her parents and the credit union.

Correct answer:

a =  2500 USD
b =  2500 USD

Step-by-step explanation:

$$\begin{gathered} x=5000 \\ {q}_1=3\%=\frac{3}{100}=0.03 \\ {q}_2=6\%=\frac{6}{100}=\frac{3}{50}=0.06 \\ 5000=a+b \\ 225=q_1\cdot a+q_2\cdot b \\ 5000=a+b \\ 225=0.03\cdot a+0.06\cdot b \\ a+b=5000 \\ 0.03a+0.06b=225 \\ Row2-0.030000000000001\cdot Row1\to Row2 \\ a+b=5000 \\ 0.03b=75 \\ b=\frac{75}{0.03}=2500 \\ a=5000-b=5000-2500=2500=2500\text{USD} \\ a=2500 \\ b=2500 \end{gathered}$$

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