To create a part for a certain piece of machinery, four equa
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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
OA E
Source: Princeton Review
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$$?\,\,\, = \,\,\,\left[ {\,{{{{360}^ \circ } - \left( {4 \cdot {{18}^ \circ }} \right)} \over {{{360}^ \circ }}}\,} \right] \cdot 100\,\,\left( \% \right)\,\,\,\mathop = \limits^{\left( * \right)} \,\,\,{4 \over 5} \cdot 100\left( \% \right)\,\,\, = \,\,\,80\left( \% \right)$$BTGmoderatorDC wrote:
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
Source: Princeton Review
$$\left( * \right)\,\,{{{{360}^ \circ } - \left( {4 \cdot {{18}^ \circ }} \right)} \over {{{360}^ \circ }}}\,\, = \,\,1 - {{4 \cdot 18} \over {2 \cdot 18 \cdot 10}}\,\, = \,\,1 - {1 \over 5}$$
We follow the notations and rationale taught in the GMATH method.
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Fabio.
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IMPORTANT: the diagrams in GMAT problem solving questions are DRAWN TO SCALE unless stated otherwise.BTGmoderatorDC wrote:
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
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 .....
Answer: E
Cheers,
Brent
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The four 18-degree shaded regions = 4*18 = 72 degrees.BTGmoderatorDC wrote:
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
The entire circle = 360 degrees.
(shaded regions)/(entire circle) = 72/360 = 1/5.
Thus:
(unshaded regions)/(entire circle) = 1 - 1/5 = 4/5 = 80%.
The correct answer is E.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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