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# Root of (16*20+8*32)=

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01 Nov 2015, 15:12
Hi EricImasogie,

While the major Radical rules won't show up too often on Test Day (you'll likely see just 1-2 questions that will involve radical rules), they are a standard part of the GMAT, so if you know the rules, then you should be able to pick up these points.

1) How long have you been studying?
2) What resources have you been using?

It might be that you need some general 'math' practice before you do too much more GMAT practice.

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27 Mar 2016, 19:05
Here is a visual that should help.
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Screen Shot 2016-03-27 at 8.04.32 PM.png [ 105.52 KiB | Viewed 1002 times ]

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04 May 2016, 08:41
Bunuel wrote:
$$\sqrt{16*20+8*32}=$$

(A) $$4\sqrt{20}$$
(B) 24
(C) 25
(D) $$4\sqrt{20}+8\sqrt{2}$$
(E) 32

Solution:

We must first simplify the expression in the square root before actually taking the square root. In other words, we have to get the product of 16 and 20 and add it to the product of 8 and 32 before taking the square root.

√[(16)(20) + (8)(32)]

√(320 + 256)

√576 = 24

Note: If struggling with determining the value of √576, we could have used the answer choices to our advantage. We need to ask ourselves what number, when squared, equals 576. Since we should have the value of 25^2 memorized, we would know that 25^2 = 625. Since 576 is slightly less than 625, we can reasonably determine that 24^2 = 576.
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04 May 2016, 09:56
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ScottTargetTestPrep wrote:
Note: If struggling with determining the value of √576, we could have used the answer choices to our advantage. We need to ask ourselves what number, when squared, equals 576. Since we should have the value of 25^2 memorized, we would know that 25^2 = 625. Since 576 is slightly less than 625, we can reasonably determine that 24^2 = 576.

$$\sqrt{576}$$

Check last digit is 6, the units digit can be 4 or 6

Check if any of the options having units digit 4 or 6, then apply the 25 rule, it can work wonders under exam hall situation...

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Updated on: 09 Jun 2016, 01:34
The first thing when you see such questions should be to simplify
16*20 + 8*32 = 320 + 256 = 576
Now, $$\sqrt{576}$$= 24

Correct Option: B

Originally posted by OptimusPrepJanielle on 08 Jun 2016, 19:42.
Last edited by OptimusPrepJanielle on 09 Jun 2016, 01:34, edited 1 time in total.
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08 Jun 2016, 21:11
Bunuel wrote:
$$\sqrt{16*20+8*32}=$$

(A) $$4\sqrt{20}$$
(B) 24
(C) 25
(D) $$4\sqrt{20}+8\sqrt{2}$$
(E) 32

Practice Questions
Question: 35
Page: 156
Difficulty: 600

$$\sqrt{16*20+8*32}=$$
$$\sqrt{16}=4 4 * [m]\sqrt{20+8*2}=$$
4 * $$\sqrt{36}=$$
4*6
24

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25 Jul 2018, 15:34
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Root of (16*20+8*32)= &nbs [#permalink] 25 Jul 2018, 15:34

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