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16 Sep 2014, 00:36
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If each blade of a windmill is 10 meters long and the endpoints of the blades rotate at a speed of \(100\pi\) meters per minute, how many revolutions per minute do the blades make? (The circumference of a circle is given by \(2\pi r\), where \(r\) is the radius).
(This question is GMAT Focus compliant. Learn More about Geometry on GMAT Focus)
A. 2
B. 3
C. 4
D. 5
E. 6
(This question is GMAT Focus compliant. Learn More about Geometry on GMAT Focus)
A. 2
B. 3
C. 4
D. 5
E. 6
16 Sep 2014, 00:36
Kudos
Bookmarks
Official Solution:
If each blade of a windmill is 10 meters long and the endpoints of the blades rotate at a speed of \(100\pi\) meters per minute, how many revolutions per minute do the blades make? (The circumference of a circle is given by \(2\pi r\), where \(r\) is the radius).
(This question is GMAT Focus compliant. [b]Learn More about Geometry on GMAT Focus) [/b]
A. 2
B. 3
C. 4
D. 5
E. 6
The circumference of a circle with a radius of 10 meters is \(20\pi\) meters, so each endpoint travels a distance of \(20\pi\) meters in one revolution. Given that the endpoints of the blades rotate at a speed of \(100 \pi\) meters per minute, they complete \(\frac{100 \pi}{20 \pi} = 5\) revolutions per minute.
Answer: D
If each blade of a windmill is 10 meters long and the endpoints of the blades rotate at a speed of \(100\pi\) meters per minute, how many revolutions per minute do the blades make? (The circumference of a circle is given by \(2\pi r\), where \(r\) is the radius).
(This question is GMAT Focus compliant. [b]Learn More about Geometry on GMAT Focus) [/b]
A. 2
B. 3
C. 4
D. 5
E. 6
The circumference of a circle with a radius of 10 meters is \(20\pi\) meters, so each endpoint travels a distance of \(20\pi\) meters in one revolution. Given that the endpoints of the blades rotate at a speed of \(100 \pi\) meters per minute, they complete \(\frac{100 \pi}{20 \pi} = 5\) revolutions per minute.
Answer: D
01 Jan 2016, 02:50
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Distance traveled in one rotation = Circumference = 2πR = πD =20 π
If blade tip travels 100 π in a minute means it has rotated 100π/20π = 5 times.
If blade tip travels 100 π in a minute means it has rotated 100π/20π = 5 times.
