A Maths Thinking Question.

Assume there is 12 bags filled with gold coins. One of the bags contain with all fake gold coins.
Mass of a gold coin is 10 gram, while the mass of fake gold coin is 9 gram.
How many times must we weigh to know which bag is the one containing all the fake gold coins?

Well a real bag would weight 1 gram heavier compare to the fake one. So if you want a simple answer it would be 12 times as you have to weight each one of the bags. But in truth it would be less or equal to 12 times. For example the 1st one might be real but the 2nd might be fake. So you might have to weight twice. Now lazy to think of an equation

Can you weigh many bags at once? then divide into 2 groups of 6. weigh one of the groups, if its 59g then divide and repeat for 2 groups of three if its 60 g then and repeat so.

So this would give minimum 3 weighs and maximum 4.