Rapid Arithmetic: Quick and Special Methods in Arithmetical Calculation

Van Nostrand, 1922 - 190 σελίδες

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Σελίδα 98 - Now .} of f- is a compound fraction, whose value is found by multiplying the numerators together for a new numerator, and the denominators for a new denominator.
Σελίδα 137 - ... a'. That is, if a number be divided into two equal parts, and also into two unequal parts, the product of the unequal parts together with the square of half their difference, is equal to the square of half the number. Bearing in mind that AC, CD are respectively half the sum and half the difference of the two lines AD, DB ; the corollary to this proposition may be expressed in the following form : " The rectangle contained by two straight lines is equal to the difference on the squares of half...
Σελίδα 105 - A decimal can be multiplied by a power of 10 by moving the decimal point to the right as many places as indicated by the power. If multiplied by 10, the decimal point is moved one place to the right; if multiplied by 100, the decimal point is moved two places to the right, and so on.
Σελίδα 113 - II.—Multiply the principal by the number of days, and divide the product by 6; then point off as in the preceding rule.
Σελίδα 98 - If the multiplicand is a compound quantity, each of its terms must be multiplied into the multiplier. Thus b-\-c-\-d into a is ab-\-ac-\-ad.
Σελίδα 105 - To multiply a decimal by 10, 100, 1000, &c., remove the decimal point as many places to the right as there are ciphers in the multiplier ; and if there be not places enough in the number, annex ciphers.
Σελίδα 86 - A number is divisible by 3 when the sum of its digits (figures) is divisible by 3 ; it is divisible by 9, when the sum of its digits is divisible by 9.
Σελίδα 159 - CA 2 : hence the area of a circle is equal to the product of the square of its radius by the constant number n, which represents the circumference whose diameter is 1, or the ratio of the circumference to the diameter.
Σελίδα 156 - Find the length of the side of a square equal in area to a circle whose circumference is 20 ft. Ans. 5-6419. 12. The diameter of the sun is 883320 miles ; what is its circumference?
Σελίδα 149 - Thus 8 to the two-thirds power, 8%, means the cube root of the square of 8; the square of 8 is 64, and the cube root of 64 is 4, so 8%='V82 = 8V64=4.

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