To compare fractions with the same denominators we look at their numerators. The one with the larger numerator is the one with the larger fraction.
Example:
Compare the two fractions and
Solution:
is larger than because the denominators are the same but the numerator is larger.
To compare fractions with different denominators, we can use cross product (or cross multiplication).
The first cross-product is the product of the first numerator and the second denominator.
The second cross-product is the product of the second numerator and the first denominator.
Then, compare the cross products using the following rules:
Example:
Compare and
Solution:
First, get the first cross product by multiplying the first numerator and the second denominator.
4 × 10 = 40 (First cross product)
Next, get the second cross product by multiplying the second numerator and the first denominator.
3 × 7 = 21 (Second cross product)
Since the first cross product is larger, the first fraction is larger.
Example:
Compare and
Solution:
First, get the first cross product by multiplying the first numerator and the second denominator.
5 × 9 = 45 (First cross product)
Next, get the second cross product by multiplying the second numerator and the first denominator.
8 × 6 = 48 (Second cross product)
The second cross product is larger, so the second fraction is larger.
The following video shows how to compare fractions using cross multiplication.
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