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Two hundred fence posts are to be placed into the ground in a straight line, 5m apart. The fence posts are stacked in a pile along this same line, 5 m from the position of the first post to be put in. Maybell is going to put inthe posts one at a time in order, and each post she puts in is farther away from the pile. Maybell can only carry one post at a time, and so she always walks back to the pile to getthe next post. If Maybell starts at the pile, how many kilometers must she walk to finish the job?

 Oct 27, 2020
 #1
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1st post walks    5 m + 5 m = 10m

 

2nd  post walks     10m + 10m = 20

 

Arithmetic sequence   d = 10   a1=10  a200 = 2000

 

 

sum    n(a1+a200)/2  = 200 (10+2000)/2 = 201000      In reality, she doesn't need to walk back after the last post is placed

 so subtract 1000     200 000 = 200 km

 Oct 27, 2020

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