Brent@GMATPrepNow wrote:alanforde800Maximus wrote:A farmer constructs a fence along the northern edge of his property, using materials such
that he places a post every 7 meters. if he uses 100 posts, how many meters will the fence span?
a)686
b)693
c)700
d)707
e)770
Please assist with above problem.
Let's look for a pattern...
1 post: fence span = 0 meters
2 posts: fence span = 7 meters
3 posts: fence span = 7 + 7 = 14 meters
4 posts: fence span = 7 + 7 + 7 = 21 meters
5 posts: fence span = 7 + 7 + 7 + 7 = 28 meters
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We can see that, for n posts, we add 7 n-1 times
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100 posts: fence span = sum of 99 sevens = (99)(7) = 693 meters
Answer:
B
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Thank you. I'm working on a similar problem. I'm trying to uncover the pattern involved.
A farmer plans to build a fence next to a stretch of driveway. Each post will be one foot wide and there will be three feet of space between each post. If the driveway is 65 feet long and the fence will be on only one side of the driveway, how many posts will the farmer need to complete the fence?
A.16
B.17
C.18
D.19
E.20
The pattern I'm seeing is:
(#) posts + 3x feet = # of feet
(1) post + 3(0) = 1 feet
(2) posts + 3(1) = 5 feet
(3) posts + 3(2) = 9 feet
(4) posts + 3(3) = 13 feet
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(17) posts + 3(16) =
65 feet
Is there another pattern that I'm not seeing in this problem? I understand the quick way to get the answer is 65/4, but I want to make sure I understand the pattern. Thanks so much.
