Is 3/4 Bigger Than 4/5?

Method 1: Common Denominators

To compare these fractions, we need a common denominator. The denominators are 4 and 5, and the least common denominator (LCD) is 20.

• Step 1. Convert \(\frac{3}{4}\): multiply numerator and denominator by 5.
  \[\frac{3}{4} = \frac{3 \times 5}{4 \times 5} = \frac{15}{20}\]
• Step 2. Convert \(\frac{4}{5}\): multiply numerator and denominator by 4.
  \[\frac{4}{5} = \frac{4 \times 4}{5 \times 4} = \frac{16}{20}\]
• Step 3. Compare the numerators: 15 vs 16.
• Step 4. Since 15 is less than 16, we know that \(\frac{3}{4} < \frac{4}{5}\).

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: \(3 \times 5 = 15\).
• Step 2. Multiply the numerator of the second fraction by the denominator of the first: \(4 \times 4 = 16\).
• Step 3. Compare the products: \(15 < 16\), so \(\frac{3}{4} < \frac{4}{5}\).

Method 3: Decimal Comparison

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

Since 0.75 is less than 0.8, we confirm that \(\frac{3}{4} < \frac{4}{5}\). In percentage terms, \(\frac{3}{4}\) is 75% and \(\frac{4}{5}\) is 80%, a difference of 5 percentage points.

Why Does This Work?

These fractions have different numerators and different denominators, so we can't compare them directly. By converting to a common denominator of 20, we're cutting both quantities into equal-sized pieces. Then 15 pieces vs 16 pieces is a straightforward comparison.