To multiply \( (1.2 \times 10^{28}) \times (3 \times 10^{-19}) \), you can separate the numerical coefficients and the powers of ten:
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Multiply the numerical coefficients: \[ 1.2 \times 3 = 3.6 \]
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Multiply the powers of ten: \[ 10^{28} \times 10^{-19} = 10^{28 + (-19)} = 10^{28 - 19} = 10^{9} \]
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Combine the results: \[ 3.6 \times 10^{9} \]
The final answer in scientific notation is: \[ \boxed{3.6 \times 10^9} \]