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Number - Operations with Fractions

Grade 6IB

Review the key concepts, formulae, and examples before starting your quiz.

πŸ”‘Concepts

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Simplifying Fractions: To simplify a fraction, divide both the numerator and the denominator by their Greatest Common Factor (GCF). Visually, this means expressing the same portion of a whole using fewer, larger pieces. For example, if you have a circle where 48\frac{4}{8} is shaded, you can see it is the same area as 12\frac{1}{2} of the circle, showing the fraction is in its simplest form when no more common factors exist.

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Equivalent Fractions: Fractions that represent the same value or part of a whole are equivalent. You can find them by multiplying or dividing the numerator and denominator by the same non-zero number. On a number line, equivalent fractions like 12\frac{1}{2}, 24\frac{2}{4}, and 48\frac{4}{8} all sit at the exact same point halfway between 00 and 11.

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Adding and Subtracting Fractions: Fractions can only be added or subtracted if they have a common denominator, representing parts of the same size. If denominators differ, find the Least Common Multiple (LCM). Visually, this is like taking two different grids (one divided into 3rds and one into 4ths) and subdividing them both into 12ths so the 'slices' are identical and can be counted together.

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Multiplying Fractions: To multiply fractions, multiply the numerators together and the denominators together. Visually, this represents taking 'a part of a part.' For example, 12Γ—34\frac{1}{2} \times \frac{3}{4} can be seen as an area model where a rectangle's width is 12\frac{1}{2} and its height is 34\frac{3}{4}; the overlapping shaded area represents the product, 38\frac{3}{8}.

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Dividing Fractions: Dividing by a fraction is equivalent to multiplying by its reciprocal (flipping the numerator and denominator). This is the 'Keep-Change-Flip' method. Visually, 12Γ·14\frac{1}{2} \div \frac{1}{4} asks 'How many quarters fit into one half?' By looking at a diagram of a half-circle, you can see that 22 quarters fit inside it, so the answer is 22.

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Mixed Numbers and Improper Fractions: An improper fraction has a numerator larger than or equal to the denominator (e.g., 53\frac{5}{3}), while a mixed number combines a whole number and a fraction (e.g., 1231\frac{2}{3}). Visually, 53\frac{5}{3} is shown as one full shape divided into 3rds plus 2 additional 3rds from a second shape.

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Comparing Fractions: To determine which fraction is larger, either convert them to a common denominator or use cross-multiplication. Visually, if you compare 23\frac{2}{3} and 34\frac{3}{4} on two identical bars, the bar representing 34\frac{3}{4} will have a slightly larger shaded region than the one representing 23\frac{2}{3}.

πŸ“Formulae

acΒ±bc=aΒ±bc\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

abΓ—cd=aΓ—cbΓ—d\frac{a}{b} \times \frac{c}{d} = \frac{a \times c}{b \times d}

abΓ·cd=abΓ—dc=adbc\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c} = \frac{ad}{bc}

wab=(wΓ—b)+abw\frac{a}{b} = \frac{(w \times b) + a}{b}

ReciprocalΒ ofΒ ab=ba\text{Reciprocal of } \frac{a}{b} = \frac{b}{a}

πŸ’‘Examples

Problem 1:

Calculate 112+351\frac{1}{2} + \frac{3}{5} and give the answer as a mixed number in its simplest form.

Solution:

Step 1: Convert the mixed number to an improper fraction: 112=(1Γ—2)+12=321\frac{1}{2} = \frac{(1 \times 2) + 1}{2} = \frac{3}{2}. \ Step 2: Find a common denominator for 22 and 55. The LCM is 1010. \ Step 3: Rewrite both fractions: 3Γ—52Γ—5=1510\frac{3 \times 5}{2 \times 5} = \frac{15}{10} and 3Γ—25Γ—2=610\frac{3 \times 2}{5 \times 2} = \frac{6}{10}. \ Step 4: Add the numerators: 1510+610=2110\frac{15}{10} + \frac{6}{10} = \frac{21}{10}. \ Step 5: Convert back to a mixed number: 2110=2110\frac{21}{10} = 2\frac{1}{10}.

Explanation:

To add these, we first convert everything to improper fractions and then find a common denominator so we are adding 'like' parts (tenths).

Problem 2:

Solve 34Γ·23\frac{3}{4} \div \frac{2}{3}.

Solution:

Step 1: Keep the first fraction: 34\frac{3}{4}. \ Step 2: Change the division sign to multiplication: Γ—\times. \ Step 3: Flip the second fraction to find its reciprocal: 32\frac{3}{2}. \ Step 4: Multiply the numerators and denominators: 3Γ—34Γ—2=98\frac{3 \times 3}{4 \times 2} = \frac{9}{8}. \ Step 5: Convert to a mixed number: 1181\frac{1}{8}.

Explanation:

Division is performed by multiplying by the reciprocal of the divisor. The result 98\frac{9}{8} shows that 23\frac{2}{3} fits into 34\frac{3}{4} one full time with a bit left over.