6 decimeters =60 centimeters =600 millimeters. Of course, a math book can't be equal to 6 decimeters or 6 centimeters, so the thickness of a math book is about 6 mm.

This question examines the knowledge points of length units.

The unit of length refers to the basic unit for regulating the length. Its international unit is "meter" (symbol "m"), and commonly used units are millimeter (mm), centimeter (cm), decimeter (dm), kilometer (km), meter (m), micron (micron) and nanometer (nm). The basic transformation relationship is as follows:

1 km =1000m =10000m =100000mm =100000mm.

So the thickness of a math book is about 6 mm

Other commonly used length units of extended data are: kilometer (km), decimeter (dm), centimeter (cm), millimeter (mm), micron (micron), nanometer (nm), picometer (pm) and femto meter (fm).

(1) km

Kilometers, abbreviated as "km", are usually used to measure the distance between two places. The commonly used conversion relationship is as follows: 1 km (km) = 1 0,000m (m) = 1 00,000m (cm) =10,000mm (mm).

(2) meters

The unit of length "meter" in the international system of units originated in France. 1790 In May, a special committee composed of French scientists suggested that one fortieth of the total length of the earth meridian passing through Paris should be used as the unit of length-meter, and this proposal was approved by the French Parliament in 179 1 year.

In order to make a benchmark to represent the value of rice, under the leadership of French astronomers Gerliangbule and Mishin, measurements were made from Dunkirk, France to Barcelona, Spain, and from 1792 to 1799. 1799, according to the measurement results, a short-section platinum rod of 3.5 mm× 25 mm was made, and the distance between the two ends of the rod was set as 1 m, which was kept by the French archives, so it was also called "archive meter". This is the earliest definition of rice.

(3) decimeter

Decimeter or dm is one of the metric units of length, and 1 decimeter is equivalent to one tenth of 1 meter. The common conversion relationship is as follows: 1 decimeter = 0.000 1 kilometer (km) = 0. 1 meter (m) = 10 centimeter (cm) = 100 millimeter (mm).

4) cm

Centimeter, unit of length; Chinese: centimeter (s), abbreviated as cm. The unit conversion of centimeters is as follows:1cm =10 mm = 0.1decimeter = 0.0 1 m = 0.0000 1 km.

(5) mm

Millimeter, also called millimeter (or gong _), is a unit of length and rainfall, and the symbol is _. 1mm is equivalent to one thousandth of 1mm (this means "milli"). The decimal relation is as follows:1mm = 0.1cm = 0.01decimeter = 0.001m = 0.000001km.

(6) Micron

Micron is a unit of length, and the symbol [micron] is pronounced [miú]. 1 micron is equivalent to one millionth of 1 meter (which means "micro").

(7) Nanometer

Nanometer (symbol is nm) is the unit of length, originally called nanometer, that is, 10-9 meters (65438+ billionth of a meter). Like centimeters, decimeters and meters, it is a unit of measurement for length. It is four times the size of an atom and less than the length of a single bacterium. A single bacterial microorganism is invisible to the naked eye, and the diameter measured by a microscope is about five microns, which is five thousand nanometers.

For example, suppose that the diameter of a hair is 0.05 mm, and it is cut into 50,000 pieces on average in the radial direction, and the thickness of each piece is about one nanometer. That is to say, one nanometer is about 0.000001mm. Nanoscience and technology, sometimes called nanotechnology, is to study the properties and applications of materials with structural dimensions ranging from 1 to 100 nm.

(8) Pimi (pm)

Pimi or pm is the unit of length, and 1 pimi is equivalent to one trillion of 1 meter. Sometimes it is called a micron in atomic physics. The conversion relationship is as follows: 1 picometer =10-12m = 0.001nanometer (nm) = 0.0000 1 micron (micron).

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