To calculate the per capita ratio of cars, we need to divide the number of cars by the number of people. However, the numbers you gave me are not in the same units. The number of people is in millions, while the number of cars is in thousands. To make them comparable, we need to convert them to the same units.
One way to do this is to use scientific notation, which is a way of writing numbers as a product of a number between 1 and 10 and a power of 10. For example, 1000 can be written as 1 x 10, and 0.01 can be written as 1 x 10.
Using scientific notation, we can write the number of people as 1.689 x 10, and the number of cars as 6.7187 x 10. Then, we can divide them by using the rule that when we divide two numbers with the same base (in this case, 10), we subtract their exponents. For example, (1 x 10) / (1 x 10) = 1 x 10 = 1 x 10 = 10.
So, the per capita ratio of cars is:
(6.7187 x 10) / (1.689 x 10) = (6.7187 / 1.689) x 10(4-7) = 3.9765 x 10
This means that for every person, there are about 0.004 cars.