SOLUTION: a railroad bridge is built over a v-shaped canyon. if the supports are 2 feet long at each end, the center support is 422 feet long, and the supports increase in length by 3 feet e
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-> SOLUTION: a railroad bridge is built over a v-shaped canyon. if the supports are 2 feet long at each end, the center support is 422 feet long, and the supports increase in length by 3 feet e
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Question 1034236: a railroad bridge is built over a v-shaped canyon. if the supports are 2 feet long at each end, the center support is 422 feet long, and the supports increase in length by 3 feet each support, what is the total length of all supports? Answer by ikleyn(52815) (Show Source):
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a railroad bridge is built over a v-shaped canyon. if the supports are 2 feet long at each end, the center support is 422 feet long,
and the supports increase in length by 3 feet each support, what is the total length of all supports?
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There are = 140 supports on one side with the lengths from 2 feet to 419 feet long,
and there is the same amount of 140 supports on the other side. Plus one central support of 422 feet long.
Combine
2 + 5 + 8 + . . . + 419 + 422
+
419 + 416 + 413 + . . . + 2
--------------------------------
422 + 422 + 422 + . . . + 422 + 422
422 feet taken 141 times. You will get the combined length 422*141 = 59502 feet, in total.
It is the "Gauss' method" for summing up an arithmetic progression.
