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by confuse mind » Tue Sep 18, 2012 8:24 pm
A road roller is used to press a ground of area 2200 sq. meter. How many rotations does it make?
I. The diameter of the road roller is 1.75 m.
II. The breadth of the road roller is 2 m.

[spoiler]
IMO - E OA - C[/spoiler]
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Source: — Data Sufficiency |
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by anusheelp » Wed Sep 19, 2012 1:32 am
confuse mind wrote:A road roller is used to press a ground of area 2200 sq. meter. How many rotations does it make?
I. The diameter of the road roller is 1.75 m.
II. The breadth of the road roller is 2 m.

[spoiler]
IMO - E OA - C[/spoiler]
Statement I gives the diameter. Hence, we can find the circumference(2*pi*r) of the circular region of the road roller.

When the road roller is rolled, each circumference acts as the length(L) of the ground it presses.

However, this alone is NOT SUFFICIENT to find the area.

Statement II tells the breadth(B) of the road roller.

Taking I and II together, we can find the area(A=L*B) covered in each rotation of the road roller.

Since the total area of the ground is given,
we can find the number of rotations required for the road roller to cover the area = 2200/A

Therefore, using I and II, we can arrive at a solution.

Hence Ans. - C
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by confuse mind » Wed Sep 19, 2012 5:37 pm
anusheelp wrote:
confuse mind wrote:A road roller is used to press a ground of area 2200 sq. meter. How many rotations does it make?
I. The diameter of the road roller is 1.75 m.
II. The breadth of the road roller is 2 m.

[spoiler]
IMO - E OA - C[/spoiler]
Statement I gives the diameter. Hence, we can find the circumference(2*pi*r) of the circular region of the road roller.

When the road roller is rolled, each circumference acts as the length(L) of the ground it presses.

However, this alone is NOT SUFFICIENT to find the area.

Statement II tells the breadth(B) of the road roller.

Taking I and II together, we can find the area(A=L*B) covered in each rotation of the road roller.

Since the total area of the ground is given,
we can find the number of rotations required for the road roller to cover the area = 2200/A

Therefore, using I and II, we can arrive at a solution.

Hence Ans. - C

Why I marked E?
Lets say, the ground is of 1 * 2200 then?
of if 11 * 200?

Thus, IMO - shape of ground is very important for deciding the number of rotations.

Experts opinion please!
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by everything's eventual » Wed Sep 19, 2012 7:18 pm
For any of the dimensions that you have mentioned, the area of the ground remains the same. Here we need to find out how much area the road roller covers during each rotation and then divide 2200 by that area to get total number of rotations.. This can be done by using both given statements.
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by everything's eventual » Wed Sep 19, 2012 7:21 pm
For example, if dimensions are 1*2200 then the road roller will need less rotations to cover the 1 m and more rotations to cover the 2200 m. If the dimensions are 11*200 then the road roller will require more rotations than previous example while covering 11 m( 11 against 1) and lesser rotations as compared to previous ecample while covering 2o0 m ( 200 against 2200). But overall rotations will remain the same as the area is the same.
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by confuse mind » Wed Sep 19, 2012 10:00 pm
everything's eventual wrote:For example, if dimensions are 1*2200 then the road roller will need less rotations to cover the 1 m and more rotations to cover the 2200 m. If the dimensions are 11*200 then the road roller will require more rotations than previous example while covering 11 m( 11 against 1) and lesser rotations as compared to previous ecample while covering 2o0 m ( 200 against 2200). But overall rotations will remain the same as the area is the same.
No...in that case it won't be possible to do it even
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by nailGmat2012 » Thu Sep 20, 2012 6:21 pm
what's the source of this question?
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by confuse mind » Thu Sep 20, 2012 11:47 pm
Still not clear....experts, please!
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