Is 2/5 Bigger Than 3/8?

Method 1: Common Denominators

To compare these fractions, we need a common denominator. The denominators are 5 and 8, and the least common denominator (LCD) is 40.

• Step 1. Convert \(\frac{2}{5}\): multiply numerator and denominator by 8.
  \[\frac{2}{5} = \frac{2 \times 8}{5 \times 8} = \frac{16}{40}\]
• Step 2. Convert \(\frac{3}{8}\): multiply numerator and denominator by 5.
  \[\frac{3}{8} = \frac{3 \times 5}{8 \times 5} = \frac{15}{40}\]
• Step 3. Compare the numerators: 16 vs 15.
• Step 4. Since 16 is greater than 15, we know that \(\frac{2}{5} > \frac{3}{8}\).

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: \(2 \times 8 = 16\).
• Step 2. Multiply the numerator of the second fraction by the denominator of the first: \(3 \times 5 = 15\).
• Step 3. Compare the products: \(16 > 15\), so \(\frac{2}{5} > \frac{3}{8}\).

Method 3: Decimal Comparison

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

Since 0.4 is greater than 0.375, we confirm that \(\frac{2}{5} > \frac{3}{8}\). In percentage terms, \(\frac{2}{5}\) is 40% and \(\frac{3}{8}\) is 37.5%, a difference of 2.5 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 40, we're cutting both quantities into equal-sized pieces. Then 16 pieces vs 15 pieces is a straightforward comparison.