Key Points

Working with Fractions

24 Sections
  • Multiplying a Fraction by a Whole Number

    To multiply a fraction by a whole number, multiply the whole number with the numerator and keep the denominator the same. For example, 5imes23=5×23=1035 imes \frac{2}{3} = \frac{5 \times 2}{3} = \frac{10}{3}.

  • Multiplication of a Fraction by a Whole Number

    To multiply a fraction by a whole number, multiply the whole number with the numerator of the fraction, keeping the denominator the same. The formula is a×bc=a×bca \times \frac{b}{c} = \frac{a \times b}{c}.

  • Multiplication of Two Fractions

    To multiply two fractions, multiply their numerators together and their denominators together. The general formula is ab×cd=a×cb×d\frac{a}{b} \times \frac{c}{d} = \frac{a \times c}{b \times d}.

  • Multiplication of Two Fractions

    The product of two fractions is found by multiplying their numerators together and their denominators together. This general rule is given by the formula ab×cd=a×cb×d\frac{a}{b} \times \frac{c}{d} = \frac{a \times c}{b \times d}.

  • The Meaning of 'Of' in Fraction Problems

    The word 'of' represents multiplication when used with fractions. For example, finding 14\frac{1}{4} of 20 means calculating 14×20=5\frac{1}{4} \times 20 = 5.

  • Multiplying Mixed Fractions

    To multiply mixed fractions, you must first convert each mixed fraction into an improper fraction. After converting, multiply the resulting improper fractions using the standard rule.

  • Simplifying Before Multiplying

    Before multiplying fractions, you can simplify by dividing any numerator and any denominator by their common factors. This process is called cancellation and makes calculations easier.

  • Simplifying by Cancelling Common Factors

    Before multiplying fractions, you can simplify by dividing any numerator and any denominator by their common factors. This process, called cancelling, makes the final multiplication easier.

  • The Meaning of 'Of' in Fraction Problems

    In word problems, the term 'of' signifies multiplication. For example, finding 25\frac{2}{5} of 20 is the same as calculating 25×20\frac{2}{5} \times 20.

  • Reciprocal of a Fraction

    The reciprocal of a fraction is found by inverting it, which means swapping the numerator and the denominator. The reciprocal of ab\frac{a}{b} is ba\frac{b}{a}, provided a0a \neq 0 and b0b \neq 0.

  • Product of a Fraction and its Reciprocal

    The product of any non-zero fraction and its reciprocal is always 1. For example, 23×32=66=1\frac{2}{3} \times \frac{3}{2} = \frac{6}{6} = 1.

  • Value of the Product of Fractions

    When you multiply two proper fractions (values between 0 and 1), the product is smaller than both of the original fractions. If you multiply a number greater than 1 by a proper fraction, the product will be smaller than the original number.

  • Reciprocal of a Fraction

    The reciprocal of a fraction is obtained by swapping its numerator and denominator. The reciprocal of ab\frac{a}{b} is ba\frac{b}{a}, where a0a \neq 0 and b0b \neq 0. The product of any fraction and its reciprocal is always 1.

  • Division of Fractions Rule

    To divide one fraction by another, you multiply the first fraction (the dividend) by the reciprocal of the second fraction (the divisor). This is often called the 'invert and multiply' rule.

  • General Formula for Fraction Division

    The formula for dividing fractions is ab÷cd=ab×dc=a×db×c\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c} = \frac{a \times d}{b \times c}. Remember to only invert the fraction you are dividing by.

  • Division of Fractions

    To divide one fraction by another, you multiply the first fraction (the dividend) by the reciprocal of the second fraction (the divisor). The rule is ab÷cd=ab×dc\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}.

  • Operations with Mixed Fractions

    Before multiplying or dividing mixed fractions, you must first convert them into improper fractions. For example, to calculate 212×342\frac{1}{2} \times \frac{3}{4}, first convert 2122\frac{1}{2} to 52\frac{5}{2}.

  • Dividing a Fraction by a Whole Number

    To divide a fraction by a whole number, multiply the fraction by the reciprocal of the whole number. For example, ab÷c=ab×1c=ab×c\frac{a}{b} \div c = \frac{a}{b} \times \frac{1}{c} = \frac{a}{b \times c}.

  • Product Size in Fraction Multiplication

    When you multiply two proper fractions (values between 0 and 1), the product is always smaller than both of the original fractions. For example, 12×13=16\frac{1}{2} \times \frac{1}{3} = \frac{1}{6}, and 16\frac{1}{6} is smaller than both 12\frac{1}{2} and 13\frac{1}{3}.

  • Dividing a Whole Number by a Fraction

    To divide a whole number by a fraction, multiply the whole number by the reciprocal of the fraction. For example, a÷bc=a×cb=a×cba \div \frac{b}{c} = a \times \frac{c}{b} = \frac{a \times c}{b}.

  • Value of the Quotient in Division

    When the divisor is a proper fraction (between 0 and 1), the quotient will be greater than the dividend. When the divisor is greater than 1, the quotient will be less than the dividend.

  • Quotient Size in Fraction Division

    When you divide by a proper fraction (a number between 0 and 1), the quotient is greater than the dividend. For example, 5÷12=105 \div \frac{1}{2} = 10, and the result 1010 is greater than the dividend 55.

  • Commutative Property of Multiplication

    The order of multiplication for fractions does not affect the final product. This means that ab×cd\frac{a}{b} \times \frac{c}{d} is equal to cd×ab\frac{c}{d} \times \frac{a}{b}.

  • Commutative Property of Multiplication

    The order in which you multiply fractions does not change the result, which is the commutative property: ab×cd=cd×ab\frac{a}{b} \times \frac{c}{d} = \frac{c}{d} \times \frac{a}{b}. Division, however, is not commutative.

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