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# Which of the following lines is perpendicular to y=(1/2)x?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6985
GMAT 1: 760 Q51 V42
GPA: 3.82
Which of the following lines is perpendicular to y=(1/2)x?  [#permalink]

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03 Sep 2018, 03:22
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15% (low)

Question Stats:

85% (00:22) correct 15% (00:35) wrong based on 39 sessions

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[Math Revolution GMAT math practice question]

Which of the following lines is perpendicular to $$y=(\frac{1}{2})x$$?

$$A. y=-2x$$
$$B. y=\frac{x}{2}$$
$$C. y=2x$$
$$D. y=\frac{-x}{2}$$
$$E. y=x$$

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Director Joined: 04 Dec 2015 Posts: 740 Location: India Concentration: Technology, Strategy Schools: ISB '19, IIMA , IIMB, XLRI WE: Information Technology (Consulting) Re: Which of the following lines is perpendicular to y=(1/2)x? [#permalink] ### Show Tags 03 Sep 2018, 03:40 1 MathRevolution wrote: [Math Revolution GMAT math practice question] Which of the following lines is perpendicular to $$y=(\frac{1}{2})x$$? $$A. y=-2x$$ $$B. y=\frac{x}{2}$$ $$C. y=2x$$ $$D. y=\frac{-x}{2}$$ $$E. y=x$$ For one line to be perpendicular to another, the relationship between their slopes has to be negative reciprocal. Slope of $$y=(\frac{1}{2})x$$ is $$= \frac{1}{2}$$ Therefore slope of perpendicular line should be $$= -2$$ $$y = -2x$$ Answer A... Director Joined: 20 Feb 2015 Posts: 795 Concentration: Strategy, General Management Re: Which of the following lines is perpendicular to y=(1/2)x? [#permalink] ### Show Tags 03 Sep 2018, 03:44 MathRevolution wrote: [Math Revolution GMAT math practice question] Which of the following lines is perpendicular to $$y=(\frac{1}{2})x$$? $$A. y=-2x$$ $$B. y=\frac{x}{2}$$ $$C. y=2x$$ $$D. y=\frac{-x}{2}$$ $$E. y=x$$ when two lines are perpendicular the product of their slops = -1 or m1*m2=-1 m1 = 1/2 m2=-2 point slope form => y=mx+c y=-2x A Intern Joined: 30 Aug 2018 Posts: 6 Re: Which of the following lines is perpendicular to y=(1/2)x? [#permalink] ### Show Tags 03 Sep 2018, 03:58 ( A ) as product of slopes of 2 perpendicular lines is -1. Posted from my mobile device GMATH Teacher Status: GMATH founder Joined: 12 Oct 2010 Posts: 772 Re: Which of the following lines is perpendicular to y=(1/2)x? [#permalink] ### Show Tags 03 Sep 2018, 05:41 MathRevolution wrote: [Math Revolution GMAT math practice question] Which of the following lines is perpendicular to $$y=(\frac{1}{2})x$$? $$A. y=-2x$$ $$B. y=\frac{x}{2}$$ $$C. y=2x$$ $$D. y=\frac{-x}{2}$$ $$E. y=x$$ Two lines are perpendicular if, and only if, they satisfy one the two geometric configurations below: 1. One of them is vertical (slope not defined) and the other is horizontal (slope is zero) 2. Both are oblique (i.e., non-horizontal and non-vertical) and, in this case, the product of their slopes must be -1. The line given in the question stem is oblique, with slope 1/2, therefore we look for a line with slope -2. Answer: A The above follows the notations and rationale taught in the GMATH method. _________________ Fabio Skilnik :: GMATH method creator (Math for the GMAT) Our high-level "quant" preparation starts here: https://gmath.net Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6985 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Which of the following lines is perpendicular to y=(1/2)x? [#permalink] ### Show Tags 05 Sep 2018, 01:17 => Two lines are perpendicular if and only if the product of their slopes is $$-1$$. Since $$(\frac{1}{2})*(-2) = -1$$, the slope of the line perpendicular to $$y = (\frac{1}{2})x$$ is $$-2$$. The only answer choice with a slope of $$-2$$ is A. Therefore, A is the answer. Answer: A _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Re: Which of the following lines is perpendicular to y=(1/2)x?   [#permalink] 05 Sep 2018, 01:17
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