In the old times...........before calculators............banks and business people would use log tables..........to multiply large numbers..

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Method 4. Multiplying Numbers Using Log Tables. Understand how to multiply numbers using their logarithms. Look up the logarithms of the two numbers you want to multiply. Add the two logarithms to find the logarithm of the solution. Look up the anti-logarithm of the result from the above step to find the solution.