Is 5/7 Bigger Than 3/8?

Method 1: Common Denominators

To compare these fractions, we need a common denominator. The denominators are 7 and 8, and the least common denominator (LCD) is 56.

• Step 1. Convert \(\frac{5}{7}\): multiply numerator and denominator by 8.
  \[\frac{5}{7} = \frac{5 \times 8}{7 \times 8} = \frac{40}{56}\]
• Step 2. Convert \(\frac{3}{8}\): multiply numerator and denominator by 7.
  \[\frac{3}{8} = \frac{3 \times 7}{8 \times 7} = \frac{21}{56}\]
• Step 3. Compare the numerators: 40 vs 21.
• Step 4. Since 40 is greater than 21, we know that \(\frac{5}{7} > \frac{3}{8}\).

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: \(5 \times 8 = 40\).
• Step 2. Multiply the numerator of the second fraction by the denominator of the first: \(3 \times 7 = 21\).
• Step 3. Compare the products: \(40 > 21\), so \(\frac{5}{7} > \frac{3}{8}\).

Method 3: Decimal Comparison

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

Since 0.714286 is greater than 0.375, we confirm that \(\frac{5}{7} > \frac{3}{8}\). In percentage terms, \(\frac{5}{7}\) is 71.4286% and \(\frac{3}{8}\) is 37.5%, a difference of 33.9286 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 56, we're cutting both quantities into equal-sized pieces. Then 40 pieces vs 21 pieces is a straightforward comparison.