39.8% of 400 + ?% of 350 = 230

Options

A. 15
B. 25
C. 18
D. 20

Answer

To solve the equation \(39.8\%\) of \(400 + ?\%\) of \(350 = 230\), we will follow these steps:

### Step 1: Approximate \(39.8\%\) to \(40\%\)
Since \(39.8\%\) is very close to \(40\%\), we can approximate it as \(40\%\) for easier calculations.

### Step 2: Calculate \(40\%\) of \(400\)
To find \(40\%\) of \(400\):
\[ 40\% \text{ of } 400 = \frac{40}{100} \times 400 = 0.4 \times 400 = 160 \]

### Step 3: Set up the equation
Now we substitute this value into the equation:
\[ 160 + ?\% \text{ of } 350 = 230 \]

### Step 4: Isolate the unknown percentage
Subtract \(160\) from both sides:
\[ ?\% \text{ of } 350 = 230 - 160 \]
\[ ?\% \text{ of } 350 = 70 \]

### Step 5: Express the unknown percentage in terms of \(x\)
Let \(x\%\) represent the unknown percentage. Therefore:
\[ \frac{x}{100} \times 350 = 70 \]

### Step 6: Solve for \(x\)
To isolate \(x\), multiply both sides by \(100\):
\[ x \times 350 = 70 \times 100 \]
\[ 350x = 7000 \]
Now, divide both sides by \(350\):
\[ x = \frac{7000}{350} \]
\[ x = 20 \]

### Conclusion
The value of \(?\%\) is \(20\%\).

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