Example

Classifying 0.5830.58\overline{3}, 0.470.47, and 3.6055512753.605551275\ldots as Rational or Irrational

Given the three numbers 0.5830.58\overline{3}, 0.470.47, and 3.6055512753.605551275\ldots, classify each as rational or irrational by inspecting its decimal form.

Rational numbers (decimals that stop or repeat):

  • 0.5830.58\overline{3}: The digit 33 repeats endlessly after 0.580.58, so this is a repeating decimal and therefore rational.
  • 0.470.47: The decimal ends after two digits, so it is a terminating decimal and therefore rational.

Irrational numbers (decimals that neither stop nor repeat):

  • 3.6055512753.605551275\ldots: The digits continue without settling into a repeating block and the decimal does not terminate, so this number is irrational.

The key strategy is to look for a terminating or repeating pattern — if one exists, the number is rational; if neither condition holds, the number is irrational.

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Updated 2026-04-21

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