To calculate the weighted mean of the student's algebra grades, we will use the weights assigned to each test:
- First Test: 80 (weight = 0.40)
- Second Test: 84 (weight = 0.40)
- Third Test: 90 (weight = 0.20)
The formula for the weighted mean is:
\[ \text{Weighted Mean} = (x_1 \cdot w_1) + (x_2 \cdot w_2) + (x_3 \cdot w_3) \]
where \(x_1\), \(x_2\), and \(x_3\) are the test scores, and \(w_1\), \(w_2\), and \(w_3\) are their corresponding weights.
Plugging in the values:
\[ \text{Weighted Mean} = (80 \cdot 0.40) + (84 \cdot 0.40) + (90 \cdot 0.20) \]
Calculating each term:
- First test: \(80 \cdot 0.40 = 32\)
- Second test: \(84 \cdot 0.40 = 33.6\)
- Third test: \(90 \cdot 0.20 = 18\)
Now, adding these values together:
\[ \text{Weighted Mean} = 32 + 33.6 + 18 = 83.6 \]
Therefore, the final grade for the student is 83.6.