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√{(4.8)(10^9)} is closest to which of the following? A. 7,000

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√{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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New post 24 Mar 2016, 17:01
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√{(4.8)(10^9)} is closest to which of the following?

A. 7,000
B. 70,000
C. 14,000
D. 22,000
E. 220,000


* A solution will be posted in two days.
[Reveal] Spoiler: OA

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Re: √{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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MathRevolution wrote:
√{(4.8)(10^9)} is closest to which of the following?

A. 7,000
B. 70,000
C. 14,000
D. 22,000
E. 220,000


* A solution will be posted in two days.



first lets get the number to slighly more friendly expression--
\(\sqrt{(4.8)*10^9}\) = \(\sqrt{48*10^8}\)
48 is nearly equal to 49 which is \(7^2\)..
so ans = \(7*10^4\)
B
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Re: √{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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New post 25 Mar 2016, 12:16
MathRevolution wrote:
√{(4.8)(10^9)} is closest to which of the following?

A. 7,000
B. 70,000
C. 14,000
D. 22,000
E. 220,000


We can apply the rule that says: √xy = (√x)(√y)
√{(4.8)(10^9)} = √{(4.8)(10^1)(10^8)}
= √{(48)(10^8)}
= (√48)(√10^8) [applied rule from above]
= (7)(10^4)
= (7)(10,000)
= 70,000

Answer: B

For more on the rule √xy = (√x)(√y), see this free video: https://www.gmatprepnow.com/module/gmat ... video/1037
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√{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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New post 25 Mar 2016, 23:19
\(\sqrt{{(4.8)(10^9)}}\)

\(\sqrt{{(48/10)(10^9)}}\)

\(\sqrt{{(48)(10^8)}}\)

\(\sqrt{{(4 * 12)(10^8)}}\)

Apply the square root:

\((2 * 2\sqrt{3})(10^4)\)

Now, \(\sqrt{3}\) = 1.73

Therefore, \(2 * 2 * 1.73 * 10^4\) = 69200 ~ 70,000

Answer: B

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Re: √{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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New post 27 Mar 2016, 01:39
√{(4.8)(10^9)} is closest to which of the following?

A. 7,000
B. 70,000
C. 14,000
D. 22,000
E. 220,000

-> √{(4.8)(10^9)}=√{(48)(10^8)}=√{(49)(10^8)}=√{(7^2)(10^4)}^2 =(7)(10^4)=70,000.
Therefore, the answer is B.
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Re: √{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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New post 28 Mar 2016, 04:53
√{(4.8)(10^9)} is closest to which of the following?

A. 7,000
B. 70,000
C. 14,000
D. 22,000
E. 220,000


-> √{(4.8)(10^9)}=√{(48)(10^8)}=√{(49)(10^8)}=√{(7^2)(10^4)^2}=(7)(10^4)=70,000
Thus, the answer is B.
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Re: √{(4.8)(10^9)} is closest to which of the following? A. 7,000 [#permalink]

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New post 24 Oct 2017, 06:08
MathRevolution wrote:
√{(4.8)(10^9)} is closest to which of the following?

A. 7,000
B. 70,000
C. 14,000
D. 22,000
E. 220,000


First, notice that in order to easily take the square root, we want to re-express 4.8 x 10^9 as 48 x 10^8. Now we have:

√{(4.8)(10^9)} = √{(48)(10^8)} = √48 x √10^8 ≈ √49 x √10^8 = 7 x 10^4 = 70,000

Answer: B
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Re: √{(4.8)(10^9)} is closest to which of the following? A. 7,000   [#permalink] 24 Oct 2017, 06:08
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