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  2. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    If the result of step 4 does not equal the result of step 5, then the original answer is wrong. If the two results match, then the original answer may be right, though it is not guaranteed to be. Example Assume the calculation 6,338 × 79, manually done, yielded a result of 500,702: Sum the digits of 6,338: (6 + 3 = 9, so count that as 0) + 3 ...

  3. List of Mersenne primes and perfect numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_Mersenne_primes...

    Perfect numbers are natural numbers that equal the sum of their positive proper divisors, which are divisors excluding the number itself. So, 6 is a perfect number because the proper divisors of 6 are 1, 2, and 3, and 1 + 2 + 3 = 6. [2] [4]

  4. Order of operations - Wikipedia

    en.wikipedia.org/wiki/Order_of_operations

    When exponents were introduced in the 16th and 17th centuries, they were given precedence over both addition and multiplication and placed as a superscript to the right of their base. [2] Thus 3 + 5 2 = 28 and 3 × 5 2 = 75. These conventions exist to avoid notational ambiguity while allowing notation to remain brief. [4]

  5. Simplification - Wikipedia

    en.wikipedia.org/wiki/Simplification

    Simplification is the process of replacing a mathematical expression by an equivalent one that is simpler (usually shorter), according to a well-founded ordering. Examples include:

  6. Irreducible fraction - Wikipedia

    en.wikipedia.org/wiki/Irreducible_fraction

    Two fractions ⁠ a / b ⁠ and ⁠ c / d ⁠ are equal or equivalent if and only if ad = bc.) For example, ⁠ 1 / 4 ⁠, ⁠ 5 / 6 ⁠, and ⁠ −101 / 100 ⁠ are all irreducible fractions. On the other hand, ⁠ 2 / 4 ⁠ is reducible since it is equal in value to ⁠ 1 / 2 ⁠, and the numerator of ⁠ 1 / 2 ⁠ is less than the numerator ...

  7. Sum of two squares theorem - Wikipedia

    en.wikipedia.org/wiki/Sum_of_two_squares_theorem

    Therefore, the theorem states that it is expressible as the sum of two squares. Indeed, 2450 = 7 2 + 49 2. The prime decomposition of the number 3430 is 2 · 5 · 7 3. This time, the exponent of 7 in the decomposition is 3, an odd number. So 3430 cannot be written as the sum of two squares.

  8. Orders of magnitude (numbers) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(numbers)

    1/52! chance of a specific shuffle Mathematics: The chances of shuffling a standard 52-card deck in any specific order is around 1.24 × 10 −68 (or exactly 1 ⁄ 52!) [4] Computing: The number 1.4 × 10 −45 is approximately equal to the smallest positive non-zero value that can be represented by a single-precision IEEE floating-point value.

  9. 49 (number) - Wikipedia

    en.wikipedia.org/wiki/49_(number)

    49 is the smallest discriminant of a totally real cubic field. [2] 49 and 94 are the only numbers below 100 whose all permutations are composites but they are not multiples of 3, repdigits or numbers which only have digits 0, 2, 4, 5, 6 and 8, even excluding the trivial one digit terms. 49 = 7^2 and 94 = 2 * 47