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Judy ran along the fence that surrounds her house. The fence forms a

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Math Expert
Joined: 02 Sep 2009
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Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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18 Sep 2016, 08:54
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Judy ran along the fence that surrounds her house. The fence forms a rectangle whose dimensions are 20×30 meters. Beginning from a vertex of the rectangle, Judy started running along one of the long sides, and stopped when she had completed running along 7 sides. This jog took her 30 seconds. What was Judy's speed in meters per second?

A. 2/3
B. 8/3
C. 23 1/3
D. 17/3
E. 6
[Reveal] Spoiler: OA

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Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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18 Sep 2016, 17:51
Judy ran 7 sides of the rectangle.
She ran one complete perimeter, then one longer side, shorter side and longer side.

Distance traveled = $$2(30+20) + 30 + 20 + 30.$$
= 180

Speed = $$\frac{Distance}{time}$$
= $$\frac{180}{30}$$
= 6 $$\frac{m}{s}$$
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Joined: 05 Sep 2015
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Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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20 Sep 2016, 00:08
4 times is perimeter.
8 times is twice perimeter.
7 times is twice perimeter minus breadth. since, she started her from run from longest side. check this while doing this kinda problems. gmat plays tricks here.
perimeter= 2(l+b) = 100.
twice perimeter= 200. 200-breadth = 180
speed 180/30 = 6.
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Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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21 Sep 2016, 19:17
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Total perimeter of the fence is 100m. Starting from the "long" side, that being 30m, the distance ran is one full loop 100m plus three of the four sides 30m + 20m + 30m = 180m. 180m/30s = $$6\frac{m}{s}$$
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Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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30 Jan 2018, 10:23
Bunuel wrote:
Judy ran along the fence that surrounds her house. The fence forms a rectangle whose dimensions are 20×30 meters. Beginning from a vertex of the rectangle, Judy started running along one of the long sides, and stopped when she had completed running along 7 sides. This jog took her 30 seconds. What was Judy's speed in meters per second?

A. 2/3
B. 8/3
C. 23 1/3
D. 17/3
E. 6

We see that Judy ran 4 long sides and 3 short sides for a total distance of 4 x 30 + 3 x 20 = 180 meters.

Since it took her 30 seconds her rate is 180/30 = 6 meters/second.

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Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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31 Jan 2018, 10:45
Bunuel wrote:
Judy ran along the fence that surrounds her house. The fence forms a rectangle whose dimensions are 20×30 meters. Beginning from a vertex of the rectangle, Judy started running along one of the long sides, and stopped when she had completed running along 7 sides. This jog took her 30 seconds. What was Judy's speed in meters per second?

A. 2/3
B. 8/3
C. 23 1/3
D. 17/3
E. 6

The total distance covered will be -
$$2* 50 + 80 = v * 30$$
$$v = 6 m/sec$$
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Intern
Joined: 01 Jan 2017
Posts: 9
Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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11 Feb 2018, 22:07
Hi all,

why are we assuming that she runs starting from the longer side?
How do we know this?
If she would start from a small side would it not be:
- Distance: 20+30+20+30 (1 full) +20+30+20 (3 sides) = 170
- Time: 30
- Speed: Distance / Time = 170/30=17/30 Answer C?
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Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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11 Feb 2018, 22:21
malcolm123 wrote:
Hi all,

why are we assuming that she runs starting from the longer side?
How do we know this?
If she would start from a small side would it not be:
- Distance: 20+30+20+30 (1 full) +20+30+20 (3 sides) = 170
- Time: 30
- Speed: Distance / Time = 170/30=17/30 Answer C?

Hi malcolm123,

Its mentioned in the question that she starts running along the longer side.
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Posts: 9
Re: Judy ran along the fence that surrounds her house. The fence forms a [#permalink]

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12 Feb 2018, 19:17
rahul16singh28 wrote:
malcolm123 wrote:
Hi all,

why are we assuming that she runs starting from the longer side?
How do we know this?
If she would start from a small side would it not be:
- Distance: 20+30+20+30 (1 full) +20+30+20 (3 sides) = 170
- Time: 30
- Speed: Distance / Time = 170/30=17/30 Answer C?

Hi malcolm123,

Its mentioned in the question that she starts running along the longer side.

Dear rahul16singh28,

thanks a million! Indeed the key to answering all questions is to slowly read the question!

Have a great day,

Malcolm

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Re: Judy ran along the fence that surrounds her house. The fence forms a   [#permalink] 12 Feb 2018, 19:17
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