Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 25 Dec 2012
Posts: 28

If 18 is 15 percent of 30 percent of a certain number, what [#permalink]
Show Tags
24 Mar 2013, 12:24
Question Stats:
84% (01:35) correct
16% (00:26) wrong based on 127 sessions
HideShow timer Statistics
If 18 is 15 percent of 30 percent of a certain number, what is the number? (A) 9 (B) 36 (C) 40 (D) 81 (E) 400 Sorry.. i'm quite sure this is a repeat but it's not showing up when i search for it.
Official Answer and Stats are available only to registered users. Register/ Login.
Last edited by exploringm on 24 Mar 2013, 14:34, edited 1 time in total.



Intern
Joined: 17 Jun 2007
Posts: 22

Re: if 18 is 15% of 30% of a certain number, what [#permalink]
Show Tags
24 Mar 2013, 13:29
1
This post received KUDOS
I'm getting E.
Got the below equation.
18=0.15(0.3*x)
By solving. x = 400.
Please explain, what's wrong.



VP
Status: Far, far away!
Joined: 02 Sep 2012
Posts: 1122
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8

Re: if 18 is 15% of 30% of a certain number, what [#permalink]
Show Tags
24 Mar 2013, 13:33
exploringm wrote: if 18 is 15 percent of 30 percent of a certain number, what is the number?
(A) 9 (B) 36 (C) 40 (D) 81 (E) 400
Maverick_Indian is right: the answer is E \(x\frac{15}{100}\frac{30}{100}=18\) \(x=18*\frac{(100*100)}{(15*30)}\) \(x=400\)
_________________
It is beyond a doubt that all our knowledge that begins with experience.
Kant , Critique of Pure Reason Tips and tricks: Inequalities , Mixture  Review: MGMAT workshop Strategy: SmartGMAT v1.0  Questions: Verbal challenge SC III CR New SC set out !! , My QuantRules for Posting in the Verbal Forum  Rules for Posting in the Quant Forum[/size][/color][/b]



Intern
Joined: 25 Dec 2012
Posts: 28

Re: if 18 is 15% of 30% of a certain number, what [#permalink]
Show Tags
24 Mar 2013, 14:29
Maverick_Indian wrote: I'm getting E.
Got the below equation.
18=0.15(0.3*x)
By solving. x = 400.
Please explain, what's wrong. My bad guys, E is the official answer. Typed it in too quickly. Thanks for the answer



Intern
Joined: 01 Feb 2013
Posts: 10
Location: United States
Concentration: Finance, Technology
GPA: 3
WE: Analyst (Computer Software)

Re: if 18 is 15% of 30% of a certain number, what [#permalink]
Show Tags
24 Mar 2013, 14:31
Estimate, 18 is 15% (approximately 1/7) 18x7 = 126. Then approximate 30% as 1/3 so 126x3=378, since the answers is so spread answer is E = 400. I would not use this method is answers is closer to each other.
_________________
Goal: 25 KUDOZ and higher scores for everyone!



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15977

Re: If 18 is 15 percent of 30 percent of a certain number, what [#permalink]
Show Tags
13 Apr 2015, 06:33
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). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 9271
Location: United States (CA)
GRE 1: 340 Q170 V170

Re: If 18 is 15 percent of 30 percent of a certain number, what [#permalink]
Show Tags
13 Apr 2015, 19:25
Hi All, The math involved in this question can be 'set up' (and dealt with) in a variety of ways. Here, if you're going to take a calculationbased approach, converting the percents to fractions would likely help you speed up (and avoid the last bit of math). We're told that 18 is 15 percent of 30 percent of a certain number. We're asked for that number. 18 = (.15)(.3)(X) 18 = (3/20)(3/10)(X) 18 = (9/200)(X) Since 9/200 is a relatively small fraction (it's far less than 10%), we know that 18 is LESS than 10% of X. Based on the given answer choices, there's only one number that is LARGE enough to fit that description.... Final Answer: GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************




Re: If 18 is 15 percent of 30 percent of a certain number, what
[#permalink]
13 Apr 2015, 19:25







