Also ignore any decimal points in the number whose logarithm you’re looking up, as the mantissa for the log of 1. Since 15 is between 10 and 100 (101 and 102), the log of 15 must be between 1 and 2, so 1. For 2. You can do this by finding the number in the body of the closest to the mantissa of this number (8699). Deletes a defined number of old records from the logs, repeating these deletions until no more old records remain. Scientists and engineers need to understand logarithms and exponents as inverse functions, and for that reason, this is a learning resource. The calculator is now an obsolete tool, having been replaced by hand held devices with virtually unlimited access to mathematical knowledge on the internet.

The first column indicates the logarithm (0, . Instead of memorizing this multiplication table, it might be better just to practice these tasks until they seem easy. The example below shows one page (of the 90) dealing with logarithms of sines, tangents, etc.

## Logarithm log records This column will show the first two or, for some large log , three digits of the number whose logarithm you’re looking up. Sometimes the numbers in this row will have a decimal point, so you’ll look up 2. This column will be the one marked with the next digit of the number whose logarithm you’re looking up.

Mentally remove it from the number you’re looking up, but make sure to write it down so you don’t forget it – it will be important later. So, the sum of the logarithms of two different numbers is the logarithm of the product of those numbers.

Now that you have the correct number of significant digits, you can use a log table as long as you deal with decimal points correctly.

While old records are being deleted, the log is locked temporarily and no new records can be added, such as during regular job execution. In spite almost universal access to calculating software, there will always be a need to quickly perform mental arithmetic. Only rarely was a division problem encountered that could not quickly be performed the old fashioned way.

The reader will recognize that this could be a homemade table since the numbers have already been calculated. For other calculations, say involving trigonometrical functions, the logarithms of the functions were tabulated.