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A racetrack bounded by two concentric circles, one with a diameter of

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A racetrack bounded by two concentric circles, one with a diameter of  [#permalink]

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New post 18 Feb 2018, 23:12
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Question Stats:

54% (02:00) correct 46% (02:29) wrong based on 81 sessions

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A racetrack bounded by two concentric circles, one with a diameter of 160 yards and the other with a diameter of 140 yards, is to covered with asphalt. If the asphalt layer is to be 1 foot deep, how many cubic yards of asphalt will be needed? (1 yard = 3 feer)

(A) \(75\pi\)

(B) \(90\pi\)

(C) \(500\pi\)

(D) \(1500\pi\)

(E) \(2000\pi\)

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Re: A racetrack bounded by two concentric circles, one with a diameter of  [#permalink]

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New post 18 Feb 2018, 23:18
Bunuel wrote:
A racetrack bounded by two concentric circles, one with a diameter of 160 yards and the other with a diameter of 140 yards, is to covered with asphalt. If the asphalt layer is to be 1 foot deep, how many cubic yards of asphalt will be needed?

(A) \(75\pi\)

(B) \(90\pi\)

(C) \(500\pi\)

(D) \(1500\pi\)

(E) \(2000\pi\)


Since the calculation required is straightforward, we'll just do it.
This is a Precise approach.

We need to calculate the area between the two circles and multiply it by a height of 1 foot = 1/3 yard.
This is \(\pi *80^2 - \pi*70^2 = 6400 \pi - 4900 \pi = 1500 \pi\).

(C), 1500/3 = 500 is our answer
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Re: A racetrack bounded by two concentric circles, one with a diameter of  [#permalink]

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New post 05 Mar 2018, 06:44
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Bunuel please edit the question if you have time. This kind of question in gmat provides always the convesion between the units feet- yards
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Re: A racetrack bounded by two concentric circles, one with a diameter of  [#permalink]

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New post 05 Mar 2018, 07:17
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Re: A racetrack bounded by two concentric circles, one with a diameter of   [#permalink] 05 Mar 2018, 07:17
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