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  2. Skip counting - Wikipedia

    en.wikipedia.org/wiki/Skip_counting

    Skip counting is a mathematics technique taught as a kind of multiplication in reform mathematics textbooks such as TERC. In older textbooks, this technique is called counting by twos (threes, fours, etc.). In skip counting by twos, a person can count to 10 by only naming every other even number: 2, 4, 6, 8, 10. [1]

  3. Serial sevens - Wikipedia

    en.wikipedia.org/wiki/Serial_sevens

    Each subtraction is considered as a unit and calculations are made on the basis of the 14 possible correct subtractions, that is 100-93-86-79-72-65-58-51-44-37-30-23-16-9-2. [ 2 ] Similar tests include serial threes where the counting downwards is done by threes, reciting the months of the year in reverse order, or spelling 'world' backwards.

  4. Counting - Wikipedia

    en.wikipedia.org/wiki/Counting

    Number blocks, which can be used for counting. Counting is the process of determining the number of elements of a finite set of objects; that is, determining the size of a set. . The traditional way of counting consists of continually increasing a (mental or spoken) counter by a unit for every element of the set, in some order, while marking (or displacing) those elements to avoid visiting the ...

  5. Yan tan tethera - Wikipedia

    en.wikipedia.org/wiki/Yan_tan_tethera

    Yan Tan Tethera or yan-tan-tethera is a sheep-counting system traditionally used by shepherds in Northern England and some other parts of Britain. [1] The words are numbers taken from Brythonic Celtic languages such as Cumbric which had died out in most of Northern England by the sixth century, but they were commonly used for sheep counting and counting stitches in knitting until the ...

  6. Proofs That Really Count - Wikipedia

    en.wikipedia.org/wiki/Proofs_That_Really_Count

    Proofs That Really Count: the Art of Combinatorial Proof is an undergraduate-level mathematics book on combinatorial proofs of mathematical identies.That is, it concerns equations between two integer-valued formulas, shown to be equal either by showing that both sides of the equation count the same type of mathematical objects, or by finding a one-to-one correspondence between the different ...

  7. Numeral system - Wikipedia

    en.wikipedia.org/wiki/Numeral_system

    In base 10, ten different digits 0, ..., 9 are used and the position of a digit is used to signify the power of ten that the digit is to be multiplied with, as in 304 = 3×100 + 0×10 + 4×1 or more precisely 3×10 2 + 0×10 1 + 4×10 0. Zero, which is not needed in the other systems, is of crucial importance here, in order to be able to "skip ...

  8. Tally marks - Wikipedia

    en.wikipedia.org/wiki/Tally_marks

    Tally marks, also called hash marks, are a form of numeral used for counting. They can be thought of as a unary numeral system. They are most useful in counting or tallying ongoing results, such as the score in a game or sport, as no intermediate results need to be erased or discarded. However, because of the length of large numbers, tallies ...

  9. Counting rods - Wikipedia

    en.wikipedia.org/wiki/Counting_rods

    In Japan, mathematicians put counting rods on a counting board, a sheet of cloth with grids, and used only vertical forms relying on the grids. An 18th-century Japanese mathematics book has a checker counting board diagram, with the order of magnitude symbols "千百十一分厘毛" (thousand, hundred, ten, unit, tenth, hundredth, thousandth). [15]