How to find defective ball from 12 balls?

If they balance, we know 12 is the fake one. Just weigh it with any other ball and figure out if it is lighter or heavier. If {8, 9} is heavier, then either 9 is heavy or 10 is light or 11 is light.

Which ball is heavier puzzle?

Three is wrong. It’s the tempting answer — weigh all the balls, four on each side. Determine which side is heavier. Then take the heavier group of four and divide them again, two on one side of the scale, and two on the other.

What is a defective ball?

We measure up balls 10 and 11 against each other and if one of them is lighter than the other, then it is the defective one. If they have the same weight, then ball 9 is the defective one.

How many defective balls are there in a puzzle?

You have 12 balls, 11 of which have the same weight. The remaining one is defective and either heavier or lighter than the rest. You can use a balance scale to compare weights in order to find which is the defective ball and whether it is heavier or lighter. How many measurement do you need so that will be surely able to do it?

How many balls do you need to make 12?

It is easy to see that if we have more than 9 balls, we need at least 3 measurements. We will prove that 3 measurements are enough for 12 balls. We place 4 balls on each side of the scale. Let balls 1, 2, 3, 4 be on the right side, and balls 5, 6, 7, 8 on the left side. CASE 1. The scale does not tip to any side.

How are the 12 balls in the brain teaser puzzle?

Conduct the second test (with the six balls that weighed heavy) with three balls on each pan. Select the three that weigh heavy. 3. select any two of the three remaining balls, and place one on each pan. If one weighs heavy, that is the out of spec ball.

What is the problem with 12 identical balls?

Question: You are give 12 identical looking balls. One of them is fake (could be heavier or lighter) than the rest of the 11 (all the others weight exactly the same). You a provided with a simple mechanical balance and you are restricted to only 3 uses. Find the fake ball. Answer: For convenience sake, let’s name the balls 1-12.