True or False? When multiplying two fractions, you first must write them with a common denominator .

False. You can multiply fractions without writing them with common denominators . It is only necessary to find a common denominator when adding or subtracting fractions.

True or False? The first step when multiplying together two mixed numbers is to convert the numbers to improper fractions.

True. When multiplying together two mixed numbers , the first step is to write both as top heavy (improper) fractions.

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Operations with Fractions (Cambridge (CIE) IGCSE International Maths: Core): Flashcards

Exam code: 0607

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FrontAdding & Subtracting Fractions
What is the lowest common denominator of two fractions.
E.g. $\frac{2}{5}$ and $\frac{1}{3}$ .

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Cards in this collection (10)

What is the lowest common denominator of two fractions.
E.g. $\frac{2}{5}$ and $\frac{1}{3}$ .
The lowest common denominator of two fractions is the smallest whole number that each denominator divides into. I.e. the lowest common multiple of the denominators.
E.g. The fractions $\frac{2}{5}$ and $\frac{1}{3}$ have denominators of 3 and 5.
Therefore, the lowest common denominator of these two fractions is 15.
True or False?
To work out $\frac{1}{4} + \frac{5}{7}$ , you add the numerators and add the denominators to get $\frac{6}{11}$ .
False.
It is a common error to add together the numerators and add together the denominators when adding fractions.
Instead, you need to first convert both fractions so that they have a common denominator and just add the numerators.
E.g. $\frac{1}{4} + \frac{5}{7} = \frac{7}{28} + \frac{20}{28} = \frac{27}{28}$ .
True or False?
When adding or subtracting fractions, sometimes you only need to change one of the denominators.
True.
When adding or subtracting fractions, if one denominator is a multiple of the other then you only need to change the smaller one.
E.g. $\frac{2}{5} + \frac{4}{15} = \frac{6}{15} + \frac{4}{15}$ .
How do you add or subtract two mixed numbers?
E.g. $5 \frac{2}{3} - 4 \frac{1}{6}$ .
It is easiest to convert the mixed numbers into improper fractions first and then complete the addition or subtraction.
E.g. $5 \frac{2}{3} - 4 \frac{1}{6}$
$\begin{array}{rcl} \frac{5 \times 3 + 2}{3} - \frac{4 \times 6 + 1}{6} & = & \frac{17}{3} - \frac{25}{6} \\ = & \frac{34}{6} - \frac{25}{6} = \frac{9}{6} = \frac{3}{2} = 1 \frac{1}{2} \end{array}$
True or False?
When multiplying two fractions, you first must write them with a common denominator.
False.
You can multiply fractions without writing them with common denominators.
It is only necessary to find a common denominator when adding or subtracting fractions.
Dividing a number by a fraction is the same as multiplying the original number by what?
Dividing a number by a fraction is the same as multiplying the original number by the reciprocal of the fraction.
For example, $9 \div \frac{2}{3} = 9 \times \frac{3}{2}$ .
How do you multiply two fractions?
E.g. $\frac{5}{8} \times \frac{3}{7}$ .
To multiply two fractions, multiply the numerators together to get the new numerator, and multiply the denominators together to get the new denominator.
E.g. $\frac{5}{8} \times \frac{3}{7} = \frac{5 \times 3}{8 \times 7} = \frac{15}{56}$
How do you divide one fraction by another fraction?
E.g. $\frac{3}{9} \div \frac{4}{5}$ .
To divide one fraction by another fraction, flip the second fraction and change the division to multiplication.
Then multiply the fractions as normal.
E.g. $\frac{3}{9} \div \frac{4}{5} = \frac{3}{9} \times \frac{5}{4} = \frac{15}{36} = \frac{5}{12}$
True or False?
When multiplying two fractions together, you can cancel out a common factor between the numerator of one fraction and the denominator of the other fraction.
E.g. $\frac{4}{15} \times \frac{25}{11} = \frac{4}{\underset{3}{15}} \times \frac{\overset{5}{25}}{11}$ .
True.
When multiplying two fractions together, you can cancel out a common factor between the numerator of one fraction and the denominator of the other fraction.
This is called cross-cancelling.
True or False?
The first step when multiplying together two mixed numbers is to convert the numbers to improper fractions.
True.
When multiplying together two mixed numbers, the first step is to write both as top heavy (improper) fractions.

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