`3.5+21xx1.3=?`

Options

A. 7.28
B. 6.13
C. 72.8
D. none of these

Answer

To solve the expression \(3.5 + 21 \times 1.3\), we will follow these steps:

### Step 1: Convert the decimal numbers to fractions
We can express \(3.5\) as \(\frac{35}{10}\) and \(1.3\) as \(\frac{13}{10}\).

### Step 2: Rewrite the expression
Now we can rewrite the expression:
\[ 3.5 + 21 \times 1.3 = \frac{35}{10} + 21 \times \frac{13}{10} \]

### Step 3: Simplify the multiplication
Next, we will calculate \(21 \times \frac{13}{10}\):
\[ 21 \times \frac{13}{10} = \frac{21 \times 13}{10} = \frac{273}{10} \]

### Step 4: Combine the fractions
Now we can add the two fractions:
\[ \frac{35}{10} + \frac{273}{10} = \frac{35 + 273}{10} = \frac{308}{10} \]

### Step 5: Simplify the final fraction
Now we simplify \(\frac{308}{10}\):
\[ \frac{308}{10} = 30.8 \]

### Final Answer
Thus, the value of \(3.5 + 21 \times 1.3\) is \(30.8\).

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