From Förberedande kurs i matematik 1

Individually, the terms are difficult to calculate, but the two logarithms can be lumped together using the logarithm law, \displaystyle \text{log }a-\text{ log }b=\text{log}\left( \frac{a}{b} \right),

\displaystyle \lg 50-\lg 5=\lg \frac{50}{5}=\lg 10=1.