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• ### $450 Tuition Credit & Official CAT Packs FREE February 15, 2019 February 15, 2019 10:00 PM EST 11:00 PM PST EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth$100 with the 3 Month Pack ($299) • ### Free GMAT practice February 15, 2019 February 15, 2019 10:00 PM EST 11:00 PM PST Instead of wasting 3 months solving 5,000+ random GMAT questions, focus on just the 1,500 you need. # To create a part for a certain piece of machinery, four equal-size wed  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics Author Message TAGS: ### Hide Tags Senior RC Moderator Status: Preparing GMAT Joined: 02 Nov 2016 Posts: 2199 Location: Pakistan GPA: 3.39 To create a part for a certain piece of machinery, four equal-size wed [#permalink] ### Show Tags Updated on: 10 May 2017, 11:16 1 00:00 Difficulty: 25% (medium) Question Stats: 81% (01:25) correct 19% (01:15) wrong based on 67 sessions ### HideShow timer Statistics Attachment: 234.jpg [ 8.56 KiB | Viewed 976 times ] To create a part for a certain piece of machinery, four equal-size wedgeshaped pieces are cut and removed from a circular piece of metal, as illustrated in the diagram above. If the unshaded portion of the circle represents the material remaining after the pieces are removed, what percentage of the original circle remains? A. 10 B. 20 C. 25 D. 60 E. 80 _________________ New Project RC Butler 2019 - Practice 2 RC Passages Everyday Final days of the GMAT Exam? => All GMAT Flashcards. This Post Helps = Press +1 Kudos Best of Luck on the GMAT!! Originally posted by SajjadAhmad on 10 May 2017, 11:13. Last edited by Bunuel on 10 May 2017, 11:16, edited 1 time in total. Edited the question. Intern Joined: 29 Apr 2017 Posts: 30 Location: India Concentration: General Management, Other WE: Engineering (Computer Software) Re: To create a part for a certain piece of machinery, four equal-size wed [#permalink] ### Show Tags 10 May 2017, 11:23 1 SajjadAhmad wrote: Attachment: 234.jpg To create a part for a certain piece of machinery, four equal-size wedgeshaped pieces are cut and removed from a circular piece of metal, as illustrated in the diagram above. If the unshaded portion of the circle represents the material remaining after the pieces are removed, what percentage of the original circle remains? A. 10 B. 20 C. 25 D. 60 E. 80 IMO, (E) is the answer. Angle subtended by the unshaded portion = 90 - 18 = 72 degree Area of the original circle remaining = Area of the 4 unshaded portions = $$\frac{4 * 72 * pi * r ^ 2}{360}$$ So, percentage of the original circle remaining = $$\frac{4 * 72 * pi * r ^ 2 * 100}{pi * r^2 * 360}$$ = 80 If you like my post, please encourage by giving KUDOS Intern Joined: 03 May 2017 Posts: 6 Schools: CBS '14 (M) To create a part for a certain piece of machinery, four equal-size wed [#permalink] ### Show Tags 10 May 2017, 12:13 Degrees in a circle: 360 4 pieces cut 18 deg each = 72 degrees cut. (Area of a circle is proportional to the angle) % of area remaining: (360-72)/360 = 4/5 ~ 80% _________________ Abhijit @ Prepitt GMAT Math Tutor MBA, Columbia Business School (Graduated 2014) GMAT Math Workshops ($90/session) | GMAT Math Private Tutoring (\$70/hr)

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Re: To create a part for a certain piece of machinery, four equal-size wed  [#permalink]

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15 May 2017, 16:33
1
Attachment:
234.jpg
To create a part for a certain piece of machinery, four equal-size wedgeshaped pieces are cut and removed from a circular piece of metal, as illustrated in the diagram above. If the unshaded portion of the circle represents the material remaining after the pieces are removed, what percentage of the original circle remains?

A. 10
B. 20
C. 25
D. 60
E. 80

Note that each shaded region corresponds to an 18 degree sector. Since there are four of these sectors, they add up to an 18 x 4 = 72-degree sector. Thus, the remaining material corresponds to a 360 - 72 = 288-degree sector. Since the entire circle has 360 degrees, the remaining material is 288/360 = 8/10 = 80% of the original circle.

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Re: To create a part for a certain piece of machinery, four equal-size wed  [#permalink]

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29 Jan 2019, 05:31
To create a part for a certain piece of machinery, four equal-size wedgeshaped pieces are cut and removed from a circular piece of metal, as illustrated in the diagram above. If the unshaded portion of the circle represents the material remaining after the pieces are removed, what percentage of the original circle remains?

A. 10
B. 20
C. 25
D. 60
E. 80

$$?\,\,\, = \,\,\,\left[ {\,{{{{360}^ \circ } - \left( {4 \cdot {{18}^ \circ }} \right)} \over {{{360}^ \circ }}}\,} \right] \cdot 100\,\,\left( \% \right)\,\,\,\mathop = \limits^{\left( * \right)} \,\,\,{4 \over 5} \cdot 100\left( \% \right)\,\,\, = \,\,\,80\left( \% \right)$$

$$\left( * \right)\,\,{{{{360}^ \circ } - \left( {4 \cdot {{18}^ \circ }} \right)} \over {{{360}^ \circ }}}\,\, = \,\,1 - {{4 \cdot 18} \over {2 \cdot 18 \cdot 10}}\,\, = \,\,1 - {1 \over 5}$$

We follow the notations and rationale taught in the GMATH method.

Regards,
Fabio.
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Re: To create a part for a certain piece of machinery, four equal-size wed  [#permalink]

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29 Jan 2019, 05:45
1
Top Contributor
Attachment:
234.jpg
To create a part for a certain piece of machinery, four equal-size wedgeshaped pieces are cut and removed from a circular piece of metal, as illustrated in the diagram above. If the unshaded portion of the circle represents the material remaining after the pieces are removed, what percentage of the original circle remains?

A. 10
B. 20
C. 25
D. 60
E. 80

IMPORTANT: the diagrams in GMAT problem solving questions are DRAWN TO SCALE unless stated otherwise.
We can use this fact to solve the question by simply "eyeballing" the diagram.

The question is basically asking us to determine what percent of the circle is NOT shaded.

Well, it's pretty obvious that at least 50% is NOT shaded.
So, we can ELIMINATE A, B and C

We're left with D (60% is NOT shaded) and E (80% is NOT shaded)
I'm pretty confident that the correct answer is MUCH closer to 80% that to 60%, so .....

Cheers,
Brent

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Re: To create a part for a certain piece of machinery, four equal-size wed   [#permalink] 29 Jan 2019, 05:45
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# To create a part for a certain piece of machinery, four equal-size wed

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