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Question

Which of the following numbers is rational?

This question was previously asked in
RRB Group D 2018 Question Paper (11-Oct-2018) (Shift 3)
The correct answer is

\(\sqrt[3]{1331}\)

\(\sqrt[3]{1331}\) is correct.

A number is called rational if it can be written as a ratio of two integers; equivalently, a root of a natural number is rational only when that natural number is a perfect power of the required order.

Step 1 — Check each option. 1221 is not a perfect square (\(34^{2} = 1156\), \(35^{2} = 1225\)), so \(\sqrt{1221}\) is irrational. 1441 is not a perfect fourth power, and 1551 is not a perfect fifth power.

Step 2 — 1331 is a perfect cube because \(11^{3} = 11 \times 11 \times 11 = 1331\), so \(\sqrt[3]{1331} = 11\), an integer and therefore rational.

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Similar Questions

  1. If the decimal number \(0.15\overline{201}\) can be expressed in the form of \(\dfrac{a}{b}\) where a and b are co-primes, then find the value of \(\sqrt{b - a + 281}\).

  2. Which of the following numbers is not an irrational number?

  3. Which of the following numbers is rational?

  4. Which of the following numbers will have a terminating decimal value?


Important Questions from Rational or Irrational Numbers

  1. Which of the following number is irrational?

  2. Which of the following numbers will have an irrational square root?

  3. What is the square root of 16 + 6√7?

  4. A non-terminating but recurring decimal is:

  5. Give the expression of   \(8.\overline{48}\)

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