Question

explain - weighed of coins one by one

Answer 1

Explanation:

First weighing: {1 2 3} vs. {4 5 6}. If the pans balance, the heavy coin is one of {7 8 9} (see below). If not, it’s on the “heavy” side of the balance (see below).

Regardless of the result of the first weighing, the heavy coin is now known to be one of three: {7 8 9} if the first weighing’s pans balanced, or {1 2 3} or {4 5 6} if not. We can say, without loss of generality, that the pans balanced in the first weighing. That leads to

Second weighing: {7} vs. {8}. If the pans balance, 9 is the heavy coin and we’re done. If not, the heavy coin is the one on the “heavy” side of the balance, and we’re done.

The same procedure can be applied to the other two possible results of the first weighing: the heavy coin can always be identified in two weighings. It is possible to find the coin in only one weighing, but you’d have to be pretty lucky: put four coins on each pan, and you’ve found the heavy one if they balance. The probability of this happening is only 1 in 9 (11%).

These questions are often asked with a twist: you don’t know whether the odd coin is heavier or lighter than the others. In cases like this, nn weighings can identify the counterfeit out of 3n−123n−12 coins, and cc coins can be evaluated in ⌈log3(2c+1)⌉⌈log3⁡(2c+1)⌉ weighings.

thankyu

plz mark my answer as brainlist....