The United States is seen as the "only industrialized country that does not use the Metric System as the primary measurement system." With the Imperial System that we use, there are points where there are major gaps in between units of measurement. For example: the amount of inches to a foot is 12, the amount of feet to a yard is 3, the amount of yards to a mile is 1,760 and the amount of ounces to a pound is 16.
Whereas in the Metric System, all the units of measurement meet at 1,000. How many millimeters are there in a meter? 1,000. Meters to a kilometer: 1,000. Grams to a kilogram: 1,000 and so on. Now, with temperature, the half-way point for water boiling in Celsius is 50 degrees. But that point in Fahrenheit is 40 since counting from 32 to 212 is an 80 degree gap, therefore it's 40.