Take 6 balls and split them into 2 groups of 3 balls each. Now you know the heavy ball is one of two possibilities. Light bulb in a room; three switches outside the room; can only go into the room once; how do you find which switch goes to the light? If one of the groups is heavier than the other group, pick 2 balls from the heavier group and use the scale to weigh them. You have 12 balls, 11 of which have the same weight. In this particular example we have 12 coins, one of them is forged and may be heavier or lighter, we don’t known which. Weigh {10} and {11}. Step 1: Choose 6 balls at random, and put 3 on each side of the balance. Using one weighing we have successfully narrowed three groups down to one. If it's not completely clear how we can make the assumption that the bad coins is in group 7,8 & 9 when the scales balance, remember we know there is a bad coin, there has to be, we have eliminated the other two groups, it … You have a set of balance scales which will give 3 possible readings: Left = Right, Left > Right, or; Left < Right (ie Left and Right have equal weight, Left is Heavier, or Left is Lighter). But I'm interested in a variation of this problem. Step 1. compare 2 groups of three balls. You have a balance and you can measure with it only 3 times to determine the different ball. How many times if you don't know whether the ball is heavier or lighter? A terrorist has implanted one of the balls with explosives, but they add such a small amount that no one can tell the difference. If one is different, we don't know whether it is heavier or lighter than the others. You don’t know that the defective one is heavier or lighter than other balls. . 2) abc < def One of a, b, c could be a lighter ball; or one of d, e, f could be a heavier ball. Interview question for Intern.8 balls the same size; one is heavier than others; how many times do you need to use a balance scale to find the ball? If one of the two balls is lighter than the other one being weighed, it is the lighter ball. Can you help? The other ball is either heavier or lighter. Step 3 If {8, 9} is heavier, then either 9 is heavy or 10 is light or 11 is light. 1- Divide them to three groups: 3, 3, and 2 balls. Now take one of the two balls that might be odd, and weigh against one of the balls you have been setting aside as 'normal'. 12 golf ball riddle 12 golf balls all appear same-one weighs slightly different-heavier or lighter scales and 3 uses. Many bowling pro shops will let you try bowling balls of different weights to determine which one is best for you. There are 12 balls, all of equal size. If they balance, 9 is fake (heavier). Lv 7. There are 8 balls. 2 weighings to find the slightly heavier ball. If the 3 balls from C didn't match the 3 balls from A in your second weighing, you now know if the unusual ball is too light or too heavy. Otherwise, the third ball is the bomb. $2$. ? Case 1. if they are both equal in weight, compare the last 2 balls - one will be heavier. Click here👆to get an answer to your question ️ 15.Two balls of different masses (one lighter and other heavier) are thrown vertically upward with the same initial speed. There are twelve identical-looking balls, but one is either heavier or lighter than the other eleven. You can also test for yourself by using house balls of different weights, although it's important to note a house ball will feel heavier than a custom-drilled ball of the same weight. Outcome 1.2: The balls do not balance. You have 12 balls all look identical (in shape, color etc.). If the scale balances, the third ball is the oddball. What's the fewest number of times you'd have to use the balance to find out which ball is different, and if it is heavier or lighter than the others. Just weigh it with any other ball and figure out if it is lighter or heavier. RickB. 1 decade ago. I know that you must weigh more than one ball on each scale and that you can get information from the good batch of balls. Then, you take the group which contains the bomb and weigh two of its balls against each other. You are also given a two-pan balance to use. If the two balls being weighed balance, the other not weighed is the lighter ball. This time the balance may be used three times to determine if there is a unique coin—and if there is, to isolate it and determine its weight relative to the others. Which one … You have 9 billiard balls, and a weighing balance. Answer: Label the balls … All of them look similar and feel the same. You have 12 identical balls. if they balance, then the other ball is the lighter or heavier one, if not that is the one ! If one outweighs the other, it is the bomb. Source(s): https://owly.im/a0fsj. If they are equal in weight, the other ball in that group is the heavy one. You can use a two sided balance system (not the electronic one). However, one of the balls is heavier or lighter. Split the balls into 4 groups of 3. If they are equal, the third ball is the heavier or lighter ball. The remaining one is defective and either heavier or lighter than the rest. 8 balls weigh the same. Weigh {8, 9} and {10, 11} (Note: 8 is surely not fake) balance - If they balance, we know 12 is the fake one. 6 - If one of the balls is heavier then we have our answer. You have 12 balls identical in size and appearance but 1 is an odd weight (could be either light or heavy). You are given 4 balls, all equal in weight except for one that is either heavier or lighter. 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