Question 60 of 480
A trader realizes 10x - x\(^2\) naira profit from the sale of x bags on corn. How many bags will give him the desired profit?
Correct Answer:
B
Explanation
To determine how many bags of corn will give the trader the desired profit, we need to analyze the profit function given in the question. The profit function is expressed as:
\[ P(x) = 10x - x^2 \]
where \( P(x) \) represents the profit in naira from selling \( x \) bags of corn.
### Step 1: Understanding the Profit Function
The profit function \( P(x) = 10x - x^2 \) is a quadratic equation. Quadratic equations generally take the form:
\[ ax^2 + bx + c \]
In our case:
- \( a = -1 \) (the coefficient of \( x^2 \))
- \( b = 10 \) (the coefficient of \( x \))
- \( c = 0 \) (there is no constant term)
### Step 2: Finding the Maximum Profit
Since the coefficient of \( x^2 \) is negative, the parabola opens downwards, which means it has a maximum point (the vertex). The x-coordinate of the vertex of a quadratic function can be found using the formula:
\[ x = -\frac{b}{2a} \]
Substituting our values for \( a \) and \( b \):
\[ x = -\frac{10}{2 \times -1} = \frac{10}{2} = 5 \]
### Step 3: Calculating the Profit at \( x = 5 \)
Now, we can calculate the profit when \( x = 5 \):
\[ P(5) = 10(5) - (5)^2 \]
\[ P(5) = 50 - 25 \]
\[ P(5) = 25 \]
This means that the maximum profit of 25 naira occurs when the trader sells 5 bags of corn.
### Step 4: Analyzing the Options
Now, let's look at the options provided:
- A. 4
- B. 5
- C. 6
- D. 7
From our calculations, we found that the maximum profit occurs at \( x = 5 \). Therefore, the correct option is:
**B. 5**
### Step 5: Why Other Options Are Incorrect
- **Option A (4)**: If we calculate the profit at \( x = 4 \):
\[ P(4) = 10(4) - (4)^2 = 40 - 16 = 24 \]
This profit is less than the maximum profit of 25 at \( x = 5 \).
- **Option C (6)**: If we calculate the profit at \( x = 6 \):
\[ P(6) = 10(6) - (6)^2 = 60 - 36 = 24 \]
Again, this profit is less than the maximum profit of 25 at \( x = 5 \).
- **Option D (7)**: If we calculate the profit at \( x = 7 \):
\[ P(7) = 10(7) - (7)^2 = 70 - 49 = 21 \]
This profit is also less than the maximum profit of 25 at \( x = 5 \).
### Summary of Key Points
- The profit function is a quadratic equation, which can be maximized.
- The maximum profit occurs at the vertex of the parabola, calculated using \( x = -\frac{b}{2a} \).
- The maximum profit of 25 naira occurs when the trader sells 5 bags of corn.
- Other options yield lower profits than the maximum profit at 5 bags.
### Revision Summary
- The profit function is \( P(x) = 10x - x^2 \).
- The maximum profit occurs at \( x = 5 \) bags.
- Profit calculations for other options (4, 6, 7) yield lower profits.
- The correct answer is **B. 5** bags.