The amount invested in each stock, the stock interest rate and the
duration of the investment, determines the interest.
Reasons:
Let X represent the sum of the amount Brian invested, we have;
Amount invested in stock paying 5% dividend = [tex]\dfrac{X}{2}[/tex]
Amount invested in stock paying 9% dividend = [tex]\dfrac{X}{2}[/tex]
Total annual interest = $420
Required:
The amount invested in the stocks
Solution:
The amount invested is found as follows;
[tex]\dfrac{X}{2} \times 5\% + \dfrac{X}{2} \times 9\% = 420[/tex]
0.025·X + 0.045·X = 420
0.07·X = 420
[tex]\displaystyle \mathrm{The \ amount \ invested , \, X} = \frac{420}{0.07} = \mathbf{ 6,000}[/tex]
The amount he invested = $6,000 ($3,000 in each stock)
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