Is 4/5 Bigger Than 4/7?

Method 1: Common Denominators

To compare these fractions, we need a common denominator. The denominators are 5 and 7, and the least common denominator (LCD) is 35.

• Step 1. Convert \(\frac{4}{5}\): multiply numerator and denominator by 7.
  \[\frac{4}{5} = \frac{4 \times 7}{5 \times 7} = \frac{28}{35}\]
• Step 2. Convert \(\frac{4}{7}\): multiply numerator and denominator by 5.
  \[\frac{4}{7} = \frac{4 \times 5}{7 \times 5} = \frac{20}{35}\]
• Step 3. Compare the numerators: 28 vs 20.
• Step 4. Since 28 is greater than 20, we know that \(\frac{4}{5} > \frac{4}{7}\).

Method 2: Cross Multiplication

A quicker way to compare fractions is to cross-multiply. Multiply each numerator by the other fraction's denominator:

• Step 1. Multiply the numerator of the first fraction by the denominator of the second: \(4 \times 7 = 28\).
• Step 2. Multiply the numerator of the second fraction by the denominator of the first: \(4 \times 5 = 20\).
• Step 3. Compare the products: \(28 > 20\), so \(\frac{4}{5} > \frac{4}{7}\).

Method 3: Decimal Comparison

Convert each fraction to a decimal by dividing the numerator by the denominator:

Since 0.8 is greater than 0.571429, we confirm that \(\frac{4}{5} > \frac{4}{7}\). In percentage terms, \(\frac{4}{5}\) is 80% and \(\frac{4}{7}\) is 57.1429%, a difference of 22.8571 percentage points.

Why Does This Work?

When two fractions have the same numerator, you have the same number of pieces — but the pieces are different sizes. A smaller denominator means each piece is larger. Since 7ths are larger pieces than 5ths, \(\frac{4}{5}\) is the bigger fraction even though both have 4 in the numerator.