# Questions tagged [weighing]

A puzzle that is centered around weighings and balances.

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### How many ways to iterate? [duplicate]

There are 9 coins, out of which one is odd, i.e. its weight is either less or more than that of the other 8 coins. How many iterations of weighing using a pan balance are required to find the odd coin ...
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### Maximize all weights

This question is related to What's the fewest weights you need to balance any weight from 1 to 40 pounds? You had 4 weights to balance any weight from $1$ to $40$ pounds which is answered previously ...
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### Which one is the poisoned pill? [duplicate]

One of my friends shared this picture to me, actually I don't know from where it came from but it seems interesting to solve. Please check below:
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### Not the Weight thing again!

John, a graduate student in US, walks into his apartment kitchen with his laptop. On the counter his roommate has left a note next to what looked like a door lock. The lock was a rectangular prism ...
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### There is a room full of balances which is in perfect balance

The 12 weights look identical and weigh 1kg,2kg,3kg......12kg.Each mark on the rod is 1m apart. Identify which weight is where and sum of marked weights
3k views

### Faulty Weight Scales

You are in a room with 3 digital weight scales and a big book. The digital scales are small like the ones you see in small stores. They are identical in all aspects. They all have a READ button which ...
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### Analytical puzzle [duplicate]

You have twelve coins. You know that one is fake. The only thing that distinguishes the fake coin from the real coins is that its weight is imperceptibly different. You have a perfectly balanced scale....
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### 1 Fake Coin among N Amount of coins

You are given $N$ coins which consists of only $1$ fake coin. You also have a sensitive old-fashioned Pan Balance Scale. You are asked to find the fake coin in totally 5 times weighing on the Pan ...
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### 30 fake coins out of 99 coins

You are given 99 coins which consists of 30 fake ones. You also have a digital balance scale with perfect precision that shows how much difference between weighs you put on. For example, if you put 10 ...
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436 views

### Weigh eight balls and find the lighter one [duplicate]

There are similar puzzles but I think this one is different. You are given eight metal balls. You know one weighs less than the rest. You are given a balance scale. What is the smallest number of ...
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### The different twins

The seesaw is filled with nine pairs of identical twins. All the kids weigh the same (e.g., they all weigh 100, but the actual numbers are irrelevant), except for one set of twins. They are still ...
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### A Two Faced Coin

A stack of 12 coins that looks identical are to be tested for the unusual one which become slightly lighter on one face and slightly heavier on the other face. If it is weighed standing on its side, ...
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### 15 Balls Sorting

This is a variant of 15 Balls Weighing. You have 15 balls of 15 different weights, but the weights are so similar you can't tell them apart by feel. The balls are also identical by any other sense ...
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### A Dozen Golden Eggs, Part 2

This is a variant of A Dozen Golden Eggs posted by TSLF, this time with the digital scale removed. You have twelve golden eggs arranged on the shelf according to shell thickness, with weight tags in ...
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### A Dozen Golden Eggs

Twelve golden eggs are arranged on the shelf according to shell thickness with weight tags in ounces. You've been told that two of the eggs were swapped by some culprit! You must put them back again ...
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### Rank the Fencers

There are five fencers. Each has a particular skill level, all of which are different. When two fencers duel, the one with the higher skill level always wins. How many duels do the fencers need to ...
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### Using a balance to determine any weight with a set of weights weighing powers of 3

There is a scale with an object on the left-hand side, whose mass is given in some number of units. Predictably, the task is to balance the two sides. But there is a catch: You only have this peculiar ...
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1 vote
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### Ball Weighing Riddle

A twist on the classic, "how many weighings to find the odd weight ball in 9 balls". Suppose there is n balls. There are two types of balls. One type weighs less than the other. In the set of balls ...
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### Evaporating coins

In the country of Dalgonia, there is only one type of fake coins and only one type of genuine coins. All genuine coins have the same weight. All fake coins have the same weight. Fake coins and ...
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232 views

### Seven Spheres of Unequal Mass, a weighing problem with a twist

You have a scale that is remarkably sturdy, and there are seven spheres of unequal mass. No sphere has the same mass as any other. There is (almost) no limit to the mass of any sphere, but the most ...
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### Thirty genuine and seventy fake coins

In the country Curgonia, there are many types of fake coins and only a single type of genuine coins. The weights of these coins satisfy the following conditions: All genuine coins have the same ...
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### 12 Coins 3 weighings generalization [duplicate]

I know the famous 12 coin, 3 weighings problem has been asked a few times already. And I saw at least one solution which can be adapted to this problem. Here's a generalisation (one of the many ...
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You have 8 identical looking rods, 2 of which are radioactive, though you don't know which. You also have a box which can test for radioactivity, which can hold any number of rods. After the test, the ...
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### Derivative of the coin weight problem [duplicate]

Most people are familiar with the following problem: A well-known example has nine (or fewer) items, say coins (or balls), that are identical in weight save for one, which in this example is lighter ...
156 views

### A pile of fakes [duplicate]

You're working in a bank and you've been given ten piles of coins. One of the piles, you've been told is a pile of fake coins. The real coins are 100g in weight, while the fake coins are just 90g. ...
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### Weighing an elephant [closed]

Here's another classic I couldn't find on the site: How can you determine the weight of an elephant without using a scale?
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### Find 2 heavy coins among 27 with a 3-pan balance

This is an extension of a previous three-pan balance puzzle. I give you a bag containing 27 coins, which look exactly the same. Among them are two fake coins. All genuine coins weigh the same. The ...
453 views

### Two heaps each with a heavy ball, and a 3-pan balance

The three-pan balance Imagine a balance with not two, but three pans. Weighings using the balance follow these rules: If there exists a pan that is lighter than each of the other two pans, then this ...
744 views

### Find 2 heavy fakes among 11 coins on a 3-pan balance

I give you 11 coins, which look exactly the same. Among them are two fake coins. All genuine coins weigh the same. The fake coins are a little heavier than the genuine ones, and they may have a ...
617 views

### Six balls, six weighings

Six spheres, six weighings. If you grow impatient with the narrative, you can skip to the TL;DR, below. An engineer was walking across the street, on the way back from lunch, when bam, hit by a bus. ...
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### A balance with three pans, detecting the lightest pan (find the one lighter/heavier ball, for a given number of balls)

This is a continuation of the questions A balance with three pans, detecting the lightest pan (find the one lighter ball) and (find the one heavier ball). There, I asked for the maximum n given a ...