What is 63^(1/2)/147^(1/2)

Why the answer isn't C?

I divide both Numerator and Denominator by 3 and I get 21/49 under square root

\(\sqrt{63} = 3\sqrt{7}\)
\(\sqrt{147} = 7\sqrt{3}\)

So, \(\frac{\sqrt{63}}{\sqrt{147}}\)

\(= 3\sqrt{7}/7\sqrt{3}\)

\(= 3\sqrt{7}*\sqrt{3}/7\sqrt{3}*\sqrt{3}\)

= \(3\sqrt{21}/7*3\)

= \(\frac{\sqrt{21}}{7}\)

Thus, answer will be (C)

+C

we must not leave square roots in denominator.

What is \(\frac{\sqrt{63}}{\sqrt{147}}\)?

\(\frac{\sqrt{63}}{\sqrt{147}}\)

\(\frac{\sqrt{7 * 3 * 3}}{\sqrt{7 * 7 *3}}\)

\(\frac{3 * \sqrt{7}}{7 * \sqrt{3}}\)

\(\frac{3 * \sqrt{7} * \sqrt{3}}{7 * \sqrt{3} * \sqrt{3}}\)

\(\frac{3 * \sqrt{21}}{7 * 3}\)

\(\frac{\sqrt{21}}{7}\)

Hence, Answer is C

Hello Abhishek009 - Why not B in this case? Are you referring to any specific rule to solve this question?

Bunuel Option B and C are the same


B) √(3/7)
C) √21/7 = √3*√7/√7*√7= √(3/7)
.

Posted from my mobile device

Yes, formatting error there. B is simply \(\frac{3}{7}\), not \(\sqrt{3/7}\). Edited. Thank you.

You can ignore this as Bunuel has changed the options.

To resolve the confusion earlier in the thread, here's a recap:

- Originally, B incorrectly said \(\sqrt{\frac{3}{7}}\)
- This is actually the same as C, just simplified differently. \(\sqrt{\frac{3}{7}}\) and \(\frac{\sqrt{21}}{7}\) have the same value - you can plug them into a calculator to check.




- The GMAT will never do this. If the answer choices are numbers, the right answer will always be the one and only answer that has the correct value. You'll never have to make a decision based on how the answer is formatted.
- Unfortunately, that means you can't eliminate answer choices just because they have a square root in the denominator (for example!).
- However, look out for situations where you simplify the answer in a certain way, and then you don't see that answer choice in the options - especially in problems that have square roots and exponents. Normally, you might assume that you got the wrong answer. However, it's possible that your answer is in the answer choices, but it's just written differently. Look out for that!

\(\frac{\sqrt{63}}{\sqrt{147}}\)

\(\sqrt{3^2 * 7} / \sqrt{7^2 * 3}\)

\(3 \sqrt{7}/7\sqrt{3}\)

Multiplying numerator and denominator with \(\sqrt{3}\)

\(3 \sqrt{7} * \sqrt{3}\)\(/ 7 * \sqrt{3}\) * \(\sqrt{3}\)

\(3 \sqrt{21} / 7 * 3\)

\(\sqrt{21}/7\) . Answer (C)...

√63/√147 < 8/12 = 0.64

A) √3/7 = 1.7/7= 0.2
B) (3/7) = 0.43
C) √21/7 = 4.6/7= 0.65
D) 3√21/7 = 1.8
E) 7/√3 = 4.1

I always prefer approximation in all such questions...

Answer Option C

'

We can simplify the given expression:

√63/√147 = (√9 x √7)/(√49 x √3) = (3√7)/(7√3)

Multiplying by √3/√3, we have:

(3√21)/21 = √21/7

Answer: C

Both B & C are correct. But now the option B has changed from \(\sqrt{3/7}\) to \(3/7\). So, wrt to current question, (C) is correct.

Both B & C are correct. But now the option B has changed from \(\sqrt{3/7}\) to \(3/7\). So, wrt to current question, (C) is correct.

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