Question 1149117
80 coins are placed in a line on the ground. The distance between any two consecutive coins is 10 metres. How far must a person travel to bring them, one by one, to a basket placed 10 metres behind the first coin. 
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You didn't say where the person started from.
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If he starts at the basket:
The 1st trip is 20 meters.
The 2nd trip is 40 meters.
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The last trip is 1600 meters.
The average trip is (1600 + 20)/2 = 810 meters
There are 80 trips
80*810 = 64800 meters