Which option correctly describes the nature of \(\frac{1}{3}+\sqrt{11}\)?
Answer and explanation
Correct answer: Irrational number
\(\sqrt{11}\) is irrational while \(\frac{1}{3}\) is rational. Assume for contradiction that \(\frac{1}{3}+\sqrt{11}\) is rational; then \(\sqrt{11}=\big(\frac{1}{3}+\sqrt{11}\big)-\frac{1}{3}\) would be a difference of two rationals and hence rational, contradicting that \(\sqrt{11}\) is irrational. Thus the sum is irrational. The closest distractor, “rational,” fails because a rational plus an irrational cannot be rational. Exam tip: when one term is irrational, directly use contradiction (subtract the rational term) to show the sum is irrational.
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What is the correct answer to this question?
Irrational number
Why is this the correct answer?
\(\sqrt{11}\) is irrational while \(\frac{1}{3}\) is rational. Assume for contradiction that \(\frac{1}{3}+\sqrt{11}\) is rational; then \(\sqrt{11}=\big(\frac{1}{3}+\sqrt{11}\big)-\frac{1}{3}\) would be a difference of two rationals and hence rational, contradicting that \(\sqrt{11}\) is irrational. Thus the sum is irrational. The closest distractor, “rational,” fails because a rational plus an irrational cannot be rational. Exam tip: when one term is irrational, directly use contradiction (subtract the rational term) to show the sum is irrational.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Polynomials. Topic: Irrational numbers and real numbers.
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