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A rancher is constructing a fence by stringing wire between posts 20 f
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24 Feb 2022, 06:40
24 Feb 2022, 06:40
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A rancher is constructing a fence by stringing wire between posts 20 feet apart. If the fence is 400 feet long, how many posts must the rancher use?
(A) 18
(B) 19
(C) 20
(D) 21
(E) 22
(A) 18
(B) 19
(C) 20
(D) 21
(E) 22
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Re: A rancher is constructing a fence by stringing wire between posts 20 f
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24 Feb 2022, 06:51
24 Feb 2022, 06:51
1
Carcass wrote:
A rancher is constructing a fence by stringing wire between posts 20 feet apart. If the fence is 400 feet long, how many posts must the rancher use?
(A) 18
(B) 19
(C) 20
(D) 21
(E) 22
(A) 18
(B) 19
(C) 20
(D) 21
(E) 22
Let's look for a pattern....
2 posts: |--|. Here, the fence length = 20 feet
3 posts: |--|--|. Here, the fence length = 20 + 20 feet
4 posts: |--|--|--|. Here, the fence length = 20 + 20 + 20 feet
5 posts: |--|--|--|--|. Here, the fence length = 20 + 20 + 20 + 20 feet (notice that the number of 20's in the sum is 1 less than the number of posts)
.
.
.
In general we can write....
n posts: |--|--|--|--|.........|--|--|. Here, the fence length = 20(n - 1)
So, if the fence length equals 400 feet we can write: 20(n - 1) = 400
Divide both sides of the equation by 20 to get: n - 1 = 20
Solve: n = 21
Answer: D
gmatclubot
Re: A rancher is constructing a fence by stringing wire between posts 20 f [#permalink]
24 Feb 2022, 06:51
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