Logic Puzzles
14. Imagine you have 10 bags full of coins, in each bag 1000
coins. In one bag, there are all coins forgeries. The original
coin is 1 gram light, forgery is 1.1 gram. Balancing just once
on an accurate weighing-machine, how can you identify the bag
with forgeries?
Solution: If there is only 1
bag with forgeries, then take 1 coin from the first bag, 2 coins
from the second bag ... ten coins from the tenth bag and weigh
the picked coins. Find out how many grams does it weigh and
compare it to the ideal state of having all original coins. The
amount of grams (the difference) is the place of the bag with
fake coins.
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