To multiply the mixed numbers -2 1/2 and -1 3/5, we first need to convert them to improper fractions.
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Convert -2 1/2: \[ -2 1/2 = -\left(2 \times 2 + 1\right)/2 = -\frac{5}{2} \]
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Convert -1 3/5: \[ -1 3/5 = -\left(1 \times 5 + 3\right)/5 = -\frac{8}{5} \]
Now we need to multiply the two improper fractions: \[ -\frac{5}{2} \times -\frac{8}{5} = \frac{5 \times 8}{2 \times 5} = \frac{40}{10} = 4 \]
The answer as a decimal is 4.
Thus, the answer is \( \boxed{4} \).