Find The Coin With 10 Boxes
One day 10 men are going to a coin factory , when they leave , the boss give them 1 box of commemorative coin for each , 1 box have 10 coins (each is 1 g), but they find that there is a box of coin that is heavier than the other coin (each is 1 g heavier than other), the boss say that if they can use the minimum times of the balance (you can see the number on the balance), they will have a 10 days break. Q: Can you find the minimum time?
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1 solution
Number the boxes as Box 1, Box 2, Box 3, . . . , Box 10. Take out 1 coin from Box 1, 2 coins from Box 2, 3 coins from Box 3 and so on 9 coins from Box 9. Now there are 45 coins. Weigh that 45 coins. If the balance shows 450 g. That means Box 1 to Box 9 are ordinary boxes and Box 10 is heavier. If balance does not show 450 g then definitely it will show more than 450 g. We will subtract 450 from the balance reading to get the box no. which is heavier. For ex - If the balance shows 454 g. That means there are 4 g extra. It is given that heavier coin is only 1 g more than ordinary coin. That means there are 4 heavier coins. It is given that there is only 1 box of heavier coin. That means those 4 coins are taken out from 1 box only and that is Box 4. So Box 4 is heavier.