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Sodium fluoride (NaF) is an inorganic compound with the formula Na F.It is a colorless or white solid that is readily soluble in water. It is used in trace amounts in the fluoridation of drinking water to prevent tooth decay, and in toothpastes and topical pharmaceuticals for the same purpose.
Putting down a tally mark for each object is another primitive method. Later, a set of objects could be tested for equality, excess or shortage—by striking out a mark and removing an object from the set. The first major advance in abstraction was the use of numerals to represent numbers. This allowed systems to be developed for recording ...
25.4 μm. A thousandth of an inch is a derived unit of length in a system of units using inches. Equal to 1000 of an inch, a thousandth is commonly called a thou / ˈθaʊ / (used for both singular and plural) or, particularly in North America, a mil (plural mils ). The words are shortened forms of the English and Latin words for "thousand ...
Solving an equation corresponds to adding and removing objects on both sides in such a way that the sides stay in balance until the only object remaining on one side is the object of unknown mass. [130] Word problems are another tool to show how algebra is applied to real-life situations. For example, students may be presented with a situation ...
Ontology is the philosophical study of being. As one of the most fundamental concepts, being encompasses all of reality and every entity within it. To articulate the basic structure of being, ontology examines what all entities have in common and how they are divided into fundamental classes, known as categories.
The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans ), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes ), all retained by Earth's gravity.
A popular size for books, dubbed AB, combines the shorter edges of A4 and B4. Another two with an aspect ratio approximating 16:9 are 20% narrower variants of A6 and B6, respectively, the latter resulting from cutting JIS B1 into 4 × 10 sheets (thus "B40"). There are also a number of traditional paper sizes, which are now used mostly by printers.
Fig. 1. HSL (a–d) and HSV (e–h). Above (a, e): cut-away 3D models of each. Below: two-dimensional plots showing two of a model's three parameters at once, holding the other constant: cylindrical shells (b, f) of constant saturation, in this case the outside surface of each cylinder; horizontal cross-sections (c, g) of constant HSL lightness or HSV value, in this case the slices halfway ...