A road roller is used to press a ground of area 2200 sq.

A road roller is used to press a ground of area 2200 sq. meter. How many rotations does it make?

(1) The diameter of the road roller is 1.75 m.
We don't know the "height" of the cylinder. for example, a cylinder with a height of 10 will have a greater surface area than a cylinder with a height of 1. The greater the surface area, the fewer the number of revolutions it would take to cover the area.
INSUFFICIENT

(2) The breadth of the road roller is 2 m.
This tells us nothing about the diameter of the roller. A very thin roller would need to make many more revolutions than a thick roller, as each revolution would cover more distance than with the smaller cylinder.
INSUFFICIENT

1+2)
d=1.75
h=2
2(3.14)*(.875^2) + 2(3.14)*(.875)*(2)
6.28*(.765) + 6.28*.875*2
4.8+10.99 = 15.79
SUFFICIENT

(C)

Hi All,

This prompt is written in an awkward way and the correct answer is debatable. With the information in the 2 Facts, we know how much ground the road-roller can press per rotation of the roller. However, the 'task' of pressing 2200 square meters of ground isn't clearly described...

1) If we're meant to figure out how long it takes to press 2200 square meters in a ROW (WITH a width of 2 meters), then the math is fairly straight-forward (and the answer is C).
2) If we're meant to THINK ABOUT how the 2200 square meters are arranged (the width might be LESS than 2 meters), then the math gets more complicated and the number of rotations would change (and the answer would be E).

Whatever this question is MEANT to be asking, the Official GMAT would present the information in a more specific, detailed fashion.

GMAT assassins aren't born, they're made,
Rich

IMO opinion answer shall be E.

The breadth and the width of the road is unknown; what if the breadth of the road is smaller than that of the roller?

Question has many assumptions.

I think, the answer is E.
The question is not clear, some detail about the ground should be there.
and just to know the number of rotations, height is not the needed variable.

Ans shd be E

How can we assume shape of ground? It could be any regular or irregular polygon, thus making the area ,in effect the specs of roller available for a certain swipe highly ambiguous that a certain pattern of pressing could be followed. Experts plz comment..highly vaguely worded un-GMAT like question.

Hi smashbiker84,

You are correct (I also discuss this issue in my post - above). Thankfully, you won't see any questions worded so 'vaguely' on the Official GMAT.

GMAT assassins aren't born, they're made,
Rich

Need to find the surface area of a cylinder. We need both the radius and the height (in this case, the height)

Hence, both statements together are sufficient.

IMO C