A circular mat with diameter 20 inches is placed...

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A circular mat with diameter 20 inches is placed on a square tabletop, each of whose sides is 24 inches long. Which of the following is closest to the fraction of the tabletop covered by the mat?

A. 5/12
B. 2/5
C. 1/2
D. 3/4
E. 5/6

The OA is C.

We know that,
$$Area_{circle}=\pi r^2=\pi\cdot10^2\approx314$$
$$Area_{square}=24^2=576$$
$$\frac{Area_{circle}}{Area_{square}}=\frac{314}{576}=\frac{157}{288}$$
Now this fraction is obviously between 1/2 and 3/4, then
$$\frac{1}{2}=\frac{144}{288}$$
and
$$\frac{3}{4}=\frac{216}{288}$$
157 is closer to 144 than to 216. Hence C is the correct option.
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by GMATGuruNY » Fri Mar 09, 2018 5:51 am
AAPL wrote:A circular mat with diameter 20 inches is placed on a square tabletop, each of whose sides is 24 inches long. Which of the following is closest to the fraction of the tabletop covered by the mat?

A. 5/12
B. 2/5
C. 1/2
D. 3/4
E. 5/6
Circle area = πr² = π(10²) ≈ 3*100.
Square area = 24*24.
(circle)/(square) ≈ (3*100)/(24*24) = (3*2*2*25)/(3*2*2*2*24) = 25/48 ≈ 24/48 = 1/2.

The correct answer is C.
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by GMATinsight » Fri Mar 09, 2018 5:53 am
AAPL wrote:A circular mat with diameter 20 inches is placed on a square tabletop, each of whose sides is 24 inches long. Which of the following is closest to the fraction of the tabletop covered by the mat?

A. 5/12
B. 2/5
C. 1/2
D. 3/4
E. 5/6

The OA is C
I would have preferred f the question had one more statement that "Centre of the Floor and Mat are at the same point. Because the question's language leaves a confusion whether some part of mat is just lying over the wall and isn't covering the maximum area of the floor.


With this ambiguity cleared, we can deduce that

Fraction of area covered = Area of Circle / . Area of the square floor = π10^2 / 24^2 = 100π / 576 = 314 / 576 = 0.55

A. 5/12 = 0.4
B. 2/5 = 0.4
C. 1/2 = 0.5
D. 3/4 = 0.75
E. 5/6 = 0.83333

Closest option is Option C
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by Jeff@TargetTestPrep » Mon Mar 12, 2018 3:49 pm
AAPL wrote:A circular mat with diameter 20 inches is placed on a square tabletop, each of whose sides is 24 inches long. Which of the following is closest to the fraction of the tabletop covered by the mat?

A. 5/12
B. 2/5
C. 1/2
D. 3/4
E. 5/6
Since the diameter of the mat is 20 inches, its radius is 10 inches. The area of the mat is:

area = πr^2 = π(10)^2 = 3.14 x 100 = 314 square inches

Since each side of the square tabletop is 24 inches long, the area is:

area = side^2 = 24 x 24 = 576 square inches

Thus, the fraction of the table covered by the mat is 314/576 = 157/288.

157/288 is about 160/290 = 16/29, which is about 1/2.

Answer: C

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