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# A thin piece of wire 40 meters long is cut into two pieces. One piece

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Intern
Joined: 10 Jun 2009
Posts: 29
Location: Stockholm, Sweden
A thin piece of wire 40 meters long is cut into two pieces. One piece  [#permalink]

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15 Jun 2009, 00:35
2
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Difficulty:

55% (hard)

Question Stats:

66% (01:19) correct 34% (01:36) wrong based on 154 sessions

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A thin piece of wire 40 meters long is cut into two pieces. One piece is used to form a circle with radius R, and the other is used to form a square. No wire is left over. Which of the following represents the total area, in square meters, of the circular and square regions in terms of R.

1) $$\pi R^2$$
2) $$\pi R^2 + 10$$
3) $$\pi R^2 + 1/4\pi^2R^2$$
4) $$\pi R^2 + (40 - 2\pi R)^2$$
5) $$\pi R^2 + (10 - 1/2\pi R)^2$$

4) or 5) is a given, I just dont see how you make the calculation necessary.

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/a-thin-piece ... 06671.html
Current Student
Joined: 03 Aug 2006
Posts: 112
Re: A thin piece of wire 40 meters long is cut into two pieces. One piece  [#permalink]

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15 Jun 2009, 01:15
2

Given:
40 meters long wire cut into two pieces.

Now Length of piece one = circumference of a circle with radius R = $$2\pi R$$

Length of piece two = perimeter of a square created using the remaining wire = $$40-2\pi R$$

$$\Rightarrow \text{length of each side of square} = \frac{40-2\pi R}{4}$$

$$= \frac{4(10-\frac{1}{2}\pi R)}{4}$$

$$= 10-\frac{1}{2}\pi R$$

Now
$$\text{Area of circle} = \pi R^2$$
$$\text {Area of square} = (10-\frac{1}{2}\pi R)^2$$

$$\text {Sum of the areas}=\pi R^2 + (10-\frac{1}{2}\pi R)^2$$
Manager
Joined: 07 Jun 2009
Posts: 185
Re: A thin piece of wire 40 meters long is cut into two pieces. One piece  [#permalink]

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15 Jun 2009, 03:01
Option 'E' is correct.
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Re: A thin piece of wire 40 meters long is cut into two pieces. One piece  [#permalink]

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07 Jan 2012, 11:49
GREAT EXPLANATION NOOKWAY. THANK YOU
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Re: A thin piece of wire 40 meters long is cut into two pieces. One piece  [#permalink]

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22 Dec 2017, 00:09
A thin piece of wire 40 meters long is cut into two pieces. One piece is used to form a circle with radius r, and the other is used to form a square. No wire is left over. Which of the following represents the total area, in square meters, of the circular and the square regions in terms of r?

A. $$\pi*r^2$$
B. $$\pi*r^2 + 10$$
C. $$\pi*r^2 + \frac{1}{4}*\pi^2*r^2$$
D. $$\pi*r^2 + (40 - 2\pi*r)^2$$
E. $$\pi*r^2 + (10 - \frac{1}{2}\pi*r)^2$$

The area of a circle will be - $$\pi{r^2}$$ and $$2\pi{r}$$ meters of wire will be used;
There will be $$40-2\pi{r}$$ meters of wire left for a square. Side of this square will be $$\frac{40-2\pi{r}}{4}=10-\frac{\pi{r}}{2}$$, hence the area of the square will be $$(10-\frac{\pi{r}}{2})^2$$.

The total area will be - $$\pi{r^2}+(10-\frac{\pi{r}}{2})^2$$.

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/a-thin-piece ... 06671.html
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Re: A thin piece of wire 40 meters long is cut into two pieces. One piece &nbs [#permalink] 22 Dec 2017, 00:09
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