The micrometre (International spelling as used by the International Bureau of Weights and Measures;[1] SI symbol: μm) or micrometer (American spelling), alsocommonly known as a micron, is an SI derived unit of length equaling 1×10−6 of ametre (SI standard prefix "micro-" = 10−6); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.000039 inch).[1] The symbol μm is sometimes rendered as um if the symbol μ cannot be used, or if the writer is not aware of the distinction.<span>[citation needed]</span>
The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria and is also commonly used in plastics manufacturing.[1] Micrometres are the standard for grading wool by the diameter of the fibres; wool finer than 25 μm can be used for garments, while coarser grades are used for outerwear, rugs, and carpets.[2] The width of a single human hair ranges from approximately 10 to 200 μm. The first and longest human chromosome is 10μm in length.
Contents <span> [hide] </span><span><span>1Examples</span><span>2SI standardization</span><span>3Symbol</span><span>4See also</span><span>5<span>Notes and references</span></span></span>
1 kilometer = 1000 meters so 12 kilometers = 12000 meters
10 laps (400 meters/lap) = 4000 meters
12000/4000 = 3
Answer: 3 days
