To multiply \(-1.7\) by \(2 \frac{1}{2}\), we first convert the mixed number \(2 \frac{1}{2}\) into an improper fraction.
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Convert \(2 \frac{1}{2}\) to an improper fraction: \[ 2 \frac{1}{2} = 2 \cdot 2 + 1 = 4 + 1 = 5 \] Thus, \[ 2 \frac{1}{2} = \frac{5}{2} \]
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Now perform the multiplication: \[ -1.7 \times \frac{5}{2} \] First, convert \(-1.7\) to a fraction: \[ -1.7 = -\frac{17}{10} \]
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Now multiply: \[ -\frac{17}{10} \times \frac{5}{2} = -\frac{17 \cdot 5}{10 \cdot 2} = -\frac{85}{20} \]
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Now simplify \(-\frac{85}{20}\): The greatest common divisor of 85 and 20 is 5. \[ -\frac{85 \div 5}{20 \div 5} = -\frac{17}{4} \]
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Convert \(-\frac{17}{4}\) to a mixed number: \(-\frac{17}{4}\) can be written as: \[ -4 \frac{1}{4} \text{ (since } 17 \div 4 = 4 \text{ remainder } 1\text{)} \]
Thus, the answer is: \[ -\mathbf{4\frac{1}{4}} \]