balance the brain

Logic Level 2

There are total of 9 eggs out of which 8 have identical weights and one has different weight. Find the minimum number of balances needed to figure out the egg with different weight.

Note : The egg with different weight has more weight than the weight of the others.

2 4 3 none of these

1 solution

Vighnesh Raut
Jun 6, 2015

Divide the eggs in $3$ groups of $3,3$ and $3$ . Then place any 2 groups of $3$ eggs on the balance.

Case 1 : The weights of the $2$ groups of $3$ eggs are equal . then we know that the heavier egg in the $3rd$ group which can be found by putting any 2 eggs from the $3rd$ group on the balance.If the weight is equal, then the heavier egg is the remaining one, and if not then the heavier egg will show more reading

Case 2 : One of the $1st$ two egg group is heavier. Then take that group and place any $2$ eggs from that group on the balance. If the weight of the eggs on the balance are equal then the heavier egg is the $3rd$ one. If unequal, then the heavier one on the balance is the required one.

$Hence$ , in either of the cases, minimum number of balances are $2$

Total eggs were 9 not 8

Ankit Raj - 5 years, 12 months ago

Thanks. I have edited the solution. At the time when I solved it, there were only $8$ eggs in the question.

Vighnesh Raut - 5 years, 9 months ago

Its still correct. The question doesn't asks for the minimum number of weighings. The minimum is 1. The case where you weigh 4 and 4 and they're both equal... The odd egg out is the heavy one.

Brian Mitchell - 4 years, 2 months ago

@Brian Mitchell – Fantastic. Can't edit comments. Please ignore my poor syntax.

Brian Mitchell - 4 years, 2 months ago

I think the question is a bit weird. It asks what is the minimum number of balances needed. That can be one. If we pick 2 groups of 4 eggs each, compare them and realize they are equal, the remaining egg is the heavier one.

Bogdan Sima - 4 years, 4 months ago

the question asks us to find minimum number of balances required to find the heavier egg in any possible scenario...... In your case, what will you do if the heavier egg is in one of the 2 groups of 4 eggs ? The question doesn't asks for the minimum number of weighing. The minimum is 1. The case where you weigh 4 and 4 and they're both equal... The odd egg out is the heavy

Vighnesh Raut - 3 years, 11 months ago

balance the brain

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