# Questions tagged [calculation-puzzle]

A puzzle that involves numerical calculations, such as multiplication and addition.

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### Analogy with Number

The given analogy is 343 : 989 :: x : 669 What is x? 223 332 333 233
51 views

### Find missing number

In below grid there are 2 numbers missing fill it with appropriate number . Text version: 69 10 13 192 ? 45 279 64 ? Hint :
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### Math Puzzle: Totaling up A,B, C [closed]

We know the following about the numbers $a$, $b$ and $c$: $$(a+b)^2=9,\quad(b+c)^2=25, \quad(a+c)^2=81$$ If $a + b + c ≥ 1$, determine the number of possible values for $a + b + c$
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### Shots, shots, shots, shots!

Once in a while I go out for a drink to my favourite bar. Normally is just drink a beer, eat some snacks and have a good time with my three friends. But last night I wanted to do some shots. The ...
182 views

### 3 x 3 Grid Square Problem

For a question that I need to answer, we have to show that there is only one arrangement for which, in a 3 x 3 grid in which the numbers from 1 to 9 are placed and 5 is the centre number, the sum of ...
172 views

### Find the missing 2 number inside inner circle

This puzzle is made by me. In the below diagram you can see there are two missing numbers; you need to fill them with the appropriate numbers.
150 views

### What is the missing number in this grid composed by 25 values?

Well, I have created a simple table with 25 values, inside it, all the data is readable, except for one that is hidden. Can you guess it? The table:
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834 views

### How to programmatically solve math puzzle

I have this puzzle and I want to solve by code. I wrote simple code trying to brute force but it fail in one condition https://dotnetfiddle.net/cJyu3w Anyone know of a link or source how to solve ...
110 views

### A Tribute to Countdown

Leave empty or put a multiplier, divider, adder or subtractor in the boxes: For example:
128 views

### Squared, what is in the post-scriptum?

Just received an invitation from a fellow mathematician for a party. The invitation is quite clear: where I need to be at what time is clearly said in the invitation, but at the bottom of the ...
110 views

### Find the missing number in the series

Numbers in the series: 4,12,14,16, ?, 25 Please help me find the missing number in the series above. I have already tried with different sequences but unable to solve this. Thanks.
34k views

### How can 64 = 65?

Here is a interesting picture with two arrangements of four shapes. How can they make a different area with the same shapes?
388 views

### Given these numbers, find the hidden word

Given this sorted list of 33 numbers, is it in your power to find the riddle they are hiding and figure out the secret word? ...
428 views

### Can you decipher these ancient numerals?

This stone was found at the foot of an ancient door. This old note with some mathematical relationships was discovered nearby. Can you use this information to figure out what number each of the 9 ...
206 views

### Six cities. What's the missing number?

Six cities are listed below. For five of them, their numerical value is given. Find the missing number. $$\text{London = 6800}$$ $$\text{Paris = 9248}$$ $$\text{Seoul = 9100}$$ $$\text{Tokyo = 7500}$$...
357 views

### 3 bags of coins, find which bag contains fake coins, doing only 1 weighing

Probably a very easy puzzle for you guys; my point is more a mathematical one. FYI, it was shown in an episode of Columbo. You have 3 bags of coins. Each bag contains 50 identical coins. Two bags ...
3k views

### How should they divide the money?

Three friends go on a picnic. John brings a loaf of sliced bread. Raj brings sliced tomatoes and Von brings a package of sliced cheese. They make sandwiches and eat them. John’s sandwich has 2 ...
20k views

### What's the fewest weights you need to balance any weight from 1 to 40 pounds?

Suppose you want to create a set of weights so that any object with an integer weight from 1 to 40 pounds can be balanced on a two-sided scale by placing a certain combination of these weights onto ...
203 views

### Picture-Puzzle. Find the number!

Make sense out of this picture below and find the two-digit number! Note: Pay attention to everything except the rounded rectangles
1k views

### Quick way to find the square root of 123.45654321?

If $n^2= 123.45654321$, then what will be the exact value of $n$? Is there a neat/efficient way to solve this without using the long division method? Since this is a GRE question, I believe there ...
526 views

### Challenge on ASCII Codes

My friend shared a challenge puzzle with me but I don't have any idea on this? I believe that it's related to ascii characters.
193 views

### Find the missing number from the pyramid

? 1 3 3 3 9 9 3 1 9 Find the missing number in the pyramid?
9k views

### Finding Day Puzzles

When the day after tomorrow becomes yesterday, the day which would then be today will be as far from Sunday as the day which is yesterday when it's two days after that day's tomorrow. What day of the ...
651 views

### 16 number puzzles on a blackboard

I have left you some number puzzles on the blackboard. Solve them and let me know what they spell. Hint:
272 views

### Catching the thief before it's too late

London, 17:15. Inspector Arbor wasn't quite happy with the current situation. Normally, he would have enjoyed this sunny Saturday outside at the Park but now wasn't the time for that. Valuable ...
316 views

### 9 8 7 6 5 4 3 2 1 = 0 and 1 2 3 4 5 6 7 8 9 = 0

There are many number sequence puzzles on this site. I acknowledge them all. Martin Gardner introduced the puzzle with the 9 digit sequence with math operations, reaching 100 as below An old ...
389 views

### Multiple XOR operations

Find $8$ distinct $8$-bit numbers, each with $4$ bits set to one, such that the cumulative XOR of these bytes is $10101010$. I imagine there are multiple answers, so the first correct answer wins the ...
95 views

### Which number is the largest in this division case? [closed]

I came across this puzzling question in a coaching school exercise book for children preparing for selective high school enrolment test. I can't figure out the answer and suspect something was wrong ...
461 views

### Cloudy with a chance of meatballs

I discovered that I can control the local weather, depending on what color shirt and hat I wear at a given location. My home country of Flanmanistan has hired me to go back and do drought and famine ...
116 views

### Banknotes recalling [closed]

Last year the inhabitants of Elfland (which are -of course- Elfs) had a referendum and decided to stop using barter and to adopt their own currency (the Elfcoin). On January 1st, 2020 the central ...
622 views

### Three shy fairies performing two thousand times

Three shy fairies participate in a dance competition. Since they are shy they don't want to be seen by anyone except for the five judges of the competition. The competition is composed of $2000$ ...
532 views

### Number puzzle i really need help with

I found this puzzle in a VRChat world. Its a 6 number puzzle, and I need to know the value of “? ? ? ? ? ?”. I also need to know the number.
419 views

### Living in prime years

A human was born somewhere in interval of [1;1920] A.D. They lived exactly 100 years. They lived through more years that were prime numbers than any other human (of the same lifespan) who was born in ...
4k views

### Men digging holes

Suppose 9 men take 9 hours to dig 9 holes in the ground. (a) How many hours would it take 3 men to dig 3 holes? (b) How many men would it take to dig 54 holes in 54 hours?
155 views

### Guess the missing digits [duplicate]

Can you guess the missing digits in the following multiplication? ??? x 3? = ???? Digits from 1 to 9 appear exactly once each. The goal is to solve it with as little calculation as possible.
2k views

### How to solve Rubik's Cube using mathematical formulas? [closed]

I am trying to solve Rubik's Cube, but it took one month for me when I started. Are there any mathematical formulas, rules and tips for solving Rubik's Cube in less time (i.e. minutes)?
189 views

### Visual calculation puzzle

Below are some objects and numbers. Try figure out what they represent and finally replace the question mark.
229 views

### Why do I celebrate later? (still 13,37 years)

A very little time ago, just a bit ago one may say, people started partying. Some even went out of their houses to do so… crazy thing, IMHO. Anyway, I don't, I'll start partying in 4886 days.¹ Why do ...
2k views

### $\tau$ is greatest! $\tau$ is all (from 1 to 20)

(This is basically an extension of $\pi$ Day puzzle one to twenty) $\tau$ is greater than $\pi$ and $\tau>\pi$. Create the numbers from $1$ to $20$ using only: Tau ($\tau$, equivalent to $2\pi$) ...
223 views

### Ten, nine, eight, seven, six, five, four, three, two, one

Some of us already did, and some of us are going to end the years with the word "teen" in it soon, for another 94 years. So let me ask the question: How many distinct numbers can you produce with ...
55k views

### A camel transporting bananas

A somewhat well-known puzzle is described as such: You have a pile of 3,000 bananas. You wish to transport them to a place 1,000 miles away on the back of a camel; however, the camel can only carry ...
391 views

### Four dice puzzle: What's the best throw?

This continues Damiano's puzzle "Four dice puzzle: 2,2,4,5" Damiano keeps throwing his four dice. After a lot of throwing and thinking and working, he has determined for every throw $a,b,c,d$ of his ...
669 views

### Four dice puzzle: 2,2,4,5

Damiano has thrown four dice and the numbers 2, 2, 4, 5 showed up on top. Damiano asks himself: What is the smallest positive integer that cannot be generated with these four numbers according to ...
14k views

### Making π from 1 2 3 4 5 6 7 8 9

There have been two other questions here and here that are similar to this one, but this changes the rules up a little. Your job is to approximate $\pi$ using the sequence of digits (in order): 1 2 ...
622 views

### What's the missing number?

$\begin{array}{ccc}6&7&4\\ 4&11&14\\ 13&2&11\\ 6&8&1\\ 15&3&?\end{array}$ Own attempt at building a puzzle, find the missing number.
248 views

### Maximizing Product of Selected Cards

Jennifer is playing a game. The Ace through King of spades are taken from a standard playing deck and laid out facedown on the table. At any time, Jennifer can select two cards and reveal them, and ...
220 views

### Two cards which product is not a square

There are 100 cards on a table numbered 1,2,...,100. What is the maximum number of cards, which can be selected such that no two cards have a product, which is a perfect square? Example: you cannot ...