If \(x = 0.\overline{12}\), what type of number is \(x\)?

Rational number

The overline shows that '12' repeats. Any repeating decimal can be expressed as a ratio of two integers, so it is rational. For example, let \(x=0.\overline{12}\). Then \(100x=12.\overline{12}\); subtracting gives \(99x=12\), hence \(x=12/99=4/33\), a fraction of integers. Choice B is wrong because irrational numbers cannot be written as a ratio of integers; here we have such a ratio. Choice C is wrong because a decimal number is real. Choice D is wrong because the value lies between 0 and 1, so it is not an integer. Exam tip: convert a repeating decimal to a fraction by multiplying to align repeats and subtracting — this quickly shows rationality.

This is a Class 10 Mathematics question. Chapter: Polynomials. Topic: Irrational numbers and real numbers.