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

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

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New post 07 Dec 2012, 02:52
5
1
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A
B
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D
E

Difficulty:

  35% (medium)

Question Stats:

72% (01:36) correct 28% (01:50) wrong based on 2814 sessions

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\(\frac{(0.0036)(2.8)}{(0.04)(0.1)(0.003)}=\)

(A) 840.0
(B) 84.0
(C) 8.4
(D) 0.84
(E) 0.084
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 07 Dec 2012, 02:58
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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


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

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

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New post 13 Jun 2013, 01:40
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While reading the problem, I re-wrote in the following way:
36/10000 * 28/10 * 100 / 4 * 10/1 * 1000/3
Simplifying further, Answer = A = 840
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 29 Oct 2013, 15:13
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I calculated the power of 10.
It was 10^5 / 10^-6.
Hence the ans. will end with 10^1. Its only A.
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 25 Aug 2014, 06:25
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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.

840 is the only answer that comes close. Answer:A

Using the approximation method you can easily solve this question in 1:30 - 2:00.
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 11 Sep 2014, 05:31
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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




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


84 /10^-1 = 840
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 23 Sep 2014, 10:09
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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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 23 Sep 2014, 23:49
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
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 24 Feb 2015, 11:26
5
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


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

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New post 28 Feb 2015, 07:26
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

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

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New post 08 Oct 2015, 07:44
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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
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 10 Oct 2015, 02:36
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

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0.0036 = 36/10,000
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New post 16 Jan 2016, 17:01
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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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 07 Sep 2016, 07:17
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
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Re: (0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 25 Nov 2017, 03:35
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Walkabout wrote:
\(\frac{(0.0036)(2.8)}{(0.04)(0.1)(0.003)}=\)

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



I multiplied all numbers by 10,000 to get integers hence

36 * 28000 / 400 * 1000* 30 = 210/ 2500 which is 0.084. Then answer is multiplied by 10,000.

0.084 *10,000 = 840

Answer A

Do you guys think it is a the fastest and the most accurate way ? :)
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(0.0036)(2.8) / (0.04)(0.1)(0.003) =  [#permalink]

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New post 25 Nov 2017, 04:05
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Walkabout wrote:
\(\frac{(0.0036)(2.8)}{(0.04)(0.1)(0.003)}=\)

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



No need to calculate for non-zero terms as it has to be 84..
check the decimal points..
Numerator has 5 and denominator has 6, so answer should be 6-5 =1 digit after decimal point
or 84*10=840
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