Ordering Surds and Radicals

CMAT 2024 · Quantitative Techniques & Data Interpretation · Medium · Surds and Indices

Arrange the following in increasing order:

A) 34\sqrt[4]{3} B) 23\sqrt[3]{2} C) 56\sqrt[6]{5} D) 76\sqrt[6]{7}

Choose the correct answer from the options given below :

  1. A.

    A < D < B < C

  2. B.

    B < C < A < D

  3. C.

    A < C < B < D

  4. D.

    B < A < C < D

Answer

B

Explanation

Take LCM of orders of radicals 4,3,6,64, 3, 6, 6, which is 1212.

A) 34=31/4=33/12=(33)1/12=271/12\sqrt[4]{3} = 3^{1/4} = 3^{3/12} = (3^3)^{1/12} = 27^{1/12} B) 23=21/3=24/12=(24)1/12=161/12\sqrt[3]{2} = 2^{1/3} = 2^{4/12} = (2^4)^{1/12} = 16^{1/12} C) 56=51/6=52/12=(52)1/12=251/12\sqrt[6]{5} = 5^{1/6} = 5^{2/12} = (5^2)^{1/12} = 25^{1/12} D) 76=71/6=72/12=(72)1/12=491/12\sqrt[6]{7} = 7^{1/6} = 7^{2/12} = (7^2)^{1/12} = 49^{1/12}

Comparing 16<25<27<49  ⟹  B<C<A<D16 < 25 < 27 < 49 \implies B < C < A < D.

Hence, Option B is correct.

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