(0.0004)(0.000005)/200,000 is equal to which of the followin

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Max@Math Revolution: Elite Legendary Member; Posts: 3991; Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members; Location: Las Vegas, USA; Thanked: 19 times

by Max@Math Revolution » Tue Dec 18, 2018 12:27 am

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[Math Revolution GMAT math practice question]

(0.0004)(0.000005)/200,000 is equal to which of the following?

A. 10^-15
B. 10^-14
C. 10^-13
D. 10^-12
E. 10^-11

Last edited by Max@Math Revolution on Mon Dec 24, 2018 6:39 am, edited 1 time in total.

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fskilnik@GMATH: GMAT Instructor; Posts: 1449; Joined: Sat Oct 09, 2010 2:16 pmFollowed by: 33 members; Thanked: 59 times

by fskilnik@GMATH » Tue Dec 18, 2018 2:04 am

Max@Math Revolution wrote: (0.0004)(0.000005)/200,000 is equal to which of the following?

A. 10^-15
B. 10^-14
C. 10^-13
D. 10^-12
E. 10^-11

$$? = {{4 \cdot {{10}^{ - 4}} \cdot 5 \cdot {{10}^{ - 6}}} \over {2 \cdot {{10}^5}}} = 10 \cdot {10^{ - 15}} = {10^{ - 14}}$$

This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.

Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Tue Dec 18, 2018 3:18 am

I believe that the answer choices should appear as shown below:

Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

(0.0004)(0.000005)/200,000 is equal to which of the following?

A. 10^-15
B. 10^-14
C. 10^-13
D. 10^-12
E. 10^-11

The blue values below cancel out, leaving only the red values:
(4 * 10¯�)(5 * 10¯�) / (20 * 10�) = 10¯¹�/10� = 10¯¹�.

The correct answer is B.

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Max@Math Revolution: Elite Legendary Member; Posts: 3991; Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members; Location: Las Vegas, USA; Thanked: 19 times

fixed

by Max@Math Revolution » Wed Dec 19, 2018 11:48 pm

=>

(0.0004)(0.000005)/200,000
= {4*5*(0.0001)(0.000001)}/{2*100,000}
= (2*10^1*10^-4*10^-6)/ (2*10^5)
= (10^-9)/(10^5) = 10^-14

Therefore, the answer is B.
Answer: B

Last edited by Max@Math Revolution on Mon Dec 24, 2018 1:09 pm, edited 1 time in total.

fskilnik@GMATH: GMAT Instructor; Posts: 1449; Joined: Sat Oct 09, 2010 2:16 pmFollowed by: 33 members; Thanked: 59 times

by fskilnik@GMATH » Thu Dec 20, 2018 2:08 am

Max@Math Revolution wrote:=>

(0.0004)(0.000005)/200,000
= {4*5*(0.0001)(0.000001)}/{2*100,000}
= (2*10^1*10^-4*10^-6)/ (2*10^5)
= (10^-9)/(10^-5) = 10^-4

Therefore, the answer is B.
Answer: B

Hi, Max!

You certainly mean:

= (10^-9)/(10^5) = 10^-14

Regards,
Fabio.

Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br

Max@Math Revolution: Elite Legendary Member; Posts: 3991; Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members; Location: Las Vegas, USA; Thanked: 19 times

by Max@Math Revolution » Mon Dec 24, 2018 1:10 pm

fskilnik@GMATH wrote:
Max@Math Revolution wrote:=>

(0.0004)(0.000005)/200,000
= {4*5*(0.0001)(0.000001)}/{2*100,000}
= (2*10^1*10^-4*10^-6)/ (2*10^5)
= (10^-9)/(10^-5) = 10^-4

Therefore, the answer is B.
Answer: B
Hi, Max!

You certainly mean:

= (10^-9)/(10^5) = 10^-14

Regards,
Fabio.

You are right. The solution and choices are fixed.
Thank you for your comments.

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8246; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Sun Mar 10, 2019 6:46 pm

Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

(0.0004)(0.000005)/200,000 is equal to which of the following?

A. 10^-15
B. 10^-14
C. 10^-13
D. 10^-12
E. 10^-11

Using scientific notation, we have:

(4 x 10^-4)(5 x 10^-6)/(2 x 10^5)

(2 x 10^-4)(5 x 10^-6)/10^5

(10^1 x 10^-10)/10^5

10^-9/10^5 = 10^-14

Answer: B

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