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# (0.0036)(2.8) / (0.04)(0.1)(0.003) =

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Manager
Joined: 02 Dec 2012
Posts: 178

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07 Dec 2012, 03:52
1
KUDOS
14
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Difficulty:

35% (medium)

Question Stats:

70% (01:17) correct 30% (01:20) wrong based on 1525 sessions

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(0.0036)(2.8) / (0.04)(0.1)(0.003) =

(A) 840.0
(B) 84.0
(C) 8.4
(D) 0.84
(E) 0.084
[Reveal] Spoiler: OA

Kudos [?]: 3460 [1], given: 0

Math Expert
Joined: 02 Sep 2009
Posts: 41872

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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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07 Dec 2012, 03:58
5
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Expert's post
10
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(0.0036)(2.8) / (0.04)(0.1)(0.003) =

(A) 840.0
(B) 84.0
(C) 8.4
(D) 0.84
(E) 0.084

$$\frac{0.0036*2.8}{0.04*0.1*0.003}=\frac{(36*10^{-4})*(28*10^{-1})}{(4*10^{-2})(1*10^{-1})*(3*10^{-3})}=\frac{36*28*10^{(-4-1)}}{4*3*10^{(-2-1-3)}}=84*10=840$$.

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SVP
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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13 Jun 2013, 02:40
4
KUDOS
While reading the problem, I re-wrote in the following way:
36/100000 * 28/10 * 100 / 4 * 10/1 * 1000/3
Simplifying further, Answer = A = 840
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Intern
Joined: 04 Aug 2013
Posts: 6

Kudos [?]: 5 [0], given: 8

Concentration: Sustainability, Entrepreneurship
WE: Architecture (Energy and Utilities)
Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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29 Oct 2013, 16:13
I calculated the power of 10.
It was 10^5 / 10^-6.
Hence the ans. will end with 10^1. Its only A.

Kudos [?]: 5 [0], given: 8

Manager
Joined: 23 May 2013
Posts: 191

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Location: United States
Concentration: Technology, Healthcare
Schools: Stanford '19 (M)
GMAT 1: 760 Q49 V45
GPA: 3.5

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25 Aug 2014, 07:25
1
KUDOS
With questions like this, take a look at the answers first. Notice the only distinction between the answers is the factor of ten; thus, an exact calculation is not necessary to solve the problem, just a quick approximation.

.0036*2.8 is ~.0036*3, which can be approximated to .01.

.04*.1 = .004

Thus we have (.01)/(.004*.003). We can cancel out the powers of ten to give us 1/(.4*.003), which is 1/(.0012).

.0012 in fraction form is 12/10,000. Thus, our answer is can be given as 10,000/12.

Using the approximation method you can easily solve this question in 1:30 - 2:00.

Kudos [?]: 107 [1], given: 42

Manager
Joined: 07 Apr 2014
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Kudos [?]: 31 [0], given: 81

Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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11 Sep 2014, 06:31
(0.0036)(2.8) / (0.04)(0.1)(0.003) =

(A) 840.0
(B) 84.0
(C) 8.4
(D) 0.84
(E) 0.084

36(28)*10^-5 / 12 * 10^-6

84 /10^-1 = 840

Kudos [?]: 31 [0], given: 81

Intern
Joined: 15 Sep 2014
Posts: 2

Kudos [?]: [0], given: 5

Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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23 Sep 2014, 11:09
I think there is mistake in the last part of the solution.
84 /10^-1 = 840 . This should be 8.4 not 840.
84/10^1 = 840.

Let me know if my understanding is correct.

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Manager
Joined: 07 Apr 2014
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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24 Sep 2014, 00:49
preetnyc wrote:
I think there is mistake in the last part of the solution.
84 /10^-1 = 840 . This should be 8.4 not 840.
84/10^1 = 840.

Let me know if my understanding is correct.

1/10^-1 = 10.. (the way i used power without symbol might create problem)

check below url..

Reciprocal in http://gmatclub.com/forum/math-number-theory-88376.html

Kudos [?]: 31 [0], given: 81

Intern
Joined: 29 Mar 2014
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Kudos [?]: 9 [2], given: 23

Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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24 Feb 2015, 12:26
2
KUDOS
1
This post was
BOOKMARKED
(0.0036)(2.8) / (0.04)(0.1)(0.003) =

(A) 840.0
(B) 84.0
(C) 8.4
(D) 0.84
(E) 0.084

With these kinds of equations the best thing to do is move the decimal places to the right, remember, what you move in the numerator has to occur in the denominator.

1) ORIGINAL EQUATION: (0.0036)(2.8) / (0.04)(0.1)(0.003)

2) MOVE 2.8 TWO PLACES TO THE RIGHT AND MOVE 0.04 TWO PLACES TO THE RIGHT, EQUATION THEN BECOMES: (0.0036)(280) / (4)(0.1)(0.003)
YOU CAN NOW DIVIDE 280 BY 4 - CANCEL OUT THE FOUR AND THE 280 BECOMES 70

3) MOVE 0.0036 ONE PLACE TO THE RIGHT AND MOVE 0.1 IN THE DENOMINATOR ONE PLACE TO THE RIGHT, EQUATION THEN BECOMES: (0.036) (70) / (1) (0.003)

4) AGAIN MOVE 0.036 TWO PLACES TO THE RIGHT AND MOVE 0.003 TWO PLACES TO THE RIGHT, EQUATION THEN BECOMES: (36)(70) / (1)(3)

5) CANCEL OUT THE THREE AND THE 36 TO FURTHER SIMPLIFY, YOUR EQUATION THEN BECOMES 12*70 = 840 WHICH IS ANSWET CHOICE A

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Optimus Prep Instructor
Joined: 06 Nov 2014
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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28 Feb 2015, 08:26
(0.0036)(2.8) / (0.04)(0.1)(0.003) =

(A) 840.0
(B) 84.0
(C) 8.4
(D) 0.84
(E) 0.084

Given that (0.0036)(2.8) / (0.04)(0.1)(0.003)
= [(36/1000)(28/10)] / [(4/100)(1/10)(3/100)]
= [(36*28)/(10000)] / [(4*1*3)/(100*10*100)]
= [(36*28)/(4*1*3)] * [(100*10*100) / 10000]
= (3*28) * 10
= 840
Hence option A

--
Optimus Prep's GMAT On Demand course for only $299 covers all verbal and quant. concepts in detail. Visit the following link to get your 7 days free trial account: http://www.optimus-prep.com/gmat-on-demand-course _________________ # Janielle Williams Customer Support Special Offer:$80-100/hr. Online Private Tutoring
GMAT On Demand Course $299 Free Online Trial Hour Kudos [?]: 522 [0], given: 23 Intern Joined: 26 Sep 2011 Posts: 1 Kudos [?]: 2 [1], given: 0 (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink] ### Show Tags 08 Oct 2015, 08:44 1 This post received KUDOS 1 This post was BOOKMARKED I found my approach to be the quickest available and I'd like to share it with you guys: (0.0036 x 2.8)/(0.04x0.1x0.003) -> expand numerator and denominator by 10^6 (since there are 5 decimal places in the numerator and 6 decimal places in the denominator) this yields: (360x28)/(4x1x3) -> cancel (120x7)/(1x1x1)= 120x7 = 840 -> A Kudos [?]: 2 [1], given: 0 Manager Joined: 18 Aug 2014 Posts: 130 Kudos [?]: 77 [0], given: 36 Location: Hong Kong Schools: Mannheim Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink] ### Show Tags 10 Oct 2015, 03:36 OptimusPrepJanielle wrote: Walkabout wrote: (0.0036)(2.8) / (0.04)(0.1)(0.003) = (A) 840.0 (B) 84.0 (C) 8.4 (D) 0.84 (E) 0.084 Given that (0.0036)(2.8) / (0.04)(0.1)(0.003) = [(36/1000)(28/10)] / [(4/100)(1/10)(3/100)] = [(36*28)/(10000)] / [(4*1*3)/(100*10*100)] = [(36*28)/(4*1*3)] * [(100*10*100) / 10000] = (3*28) * 10 = 840 Hence option A -- Optimus Prep's GMAT On Demand course for only$299 covers all verbal and quant. concepts in detail. Visit the following link to get your 7 days free trial account: http://www.optimus-prep.com/gmat-on-demand-course

0.0036 = 36/10,000

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Manager
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16 Jan 2016, 18:01
Not sure if this is the right way to approach the answer, since the answer choices have big separation, I decided to approximate.
(0.0036)(2.8) / (0.04)(0.1)(0.003) = (4∗10^−3)∗(3)/[(4∗10^−2)(1∗10^−1)∗(3∗10^−3)] = 1*10^3 = ~1000
Closest Ans to 1000 is C: 840
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If you analyze enough data, you can predict the future.....its calculating probability, nothing more!

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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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07 Sep 2016, 08:17
i put everything in fractions, and it helped much.
[(36*28)/10,000 * 10] * (100*10*1000)/(4*1*3)

now, simplify and get 7*12*10 = 840
A

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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) = [#permalink]

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29 Sep 2017, 08:43
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =   [#permalink] 29 Sep 2017, 08:43
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