The absolute value measures the <u>distance of a point or a function to the origin</u>.
One example of inequality is:
Which has solution:
In this problem:
Bolts with a diameter of 6.5 mm, with a tolerance of 0.04 mm, thus the <u>absolute value of the difference of the diameter D and 6.5 has to be of at most 0.04</u>, that is: