Questions tagged [calculation-puzzle]

A puzzle that involves numerical calculations, such as multiplication and addition. Use with the [mathematics] tag.

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1,1,1,-17,? What's the next number and what's the pattern [closed]

1,1,1,-17,? What is the pattern and what number comes next
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4 votes
1 answer
104 views

Find the 3 Item Amounts

Last week the store's receipt printer removed lines randomly from each item amount. A technician repaired the printer, but now it adds lines randomly to each item amount! The cashier told me that for ...
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  • 15k
8 votes
2 answers
551 views

A number association puzzle

These 0 to 10 digits are associated with the specific numbers as shown below. What are the associated numbers for digits 9 and 10? Why? Bonus: Is there an associated number for 11?
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  • 615
18 votes
3 answers
702 views

Find the Two Item Amounts

I bought 2 items yesterday and the receipt was incorrect, so I asked the cashier about it. She told me that The receipt printer had been acting funny recently. The total is always correct, but some ...
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  • 15k
-2 votes
0 answers
103 views

Decipher this using a clock

A friend gave me this encrypted message: INAS 130356G HBAV 15009RA 9999 VCJ048 04/00 H2945 YTR HV2 ZSW956 A00401002 400780033 AZUV There's a hint: Like in the real world, a time on the clock can be ...
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2 votes
1 answer
677 views

What is 12 in this same pattern?

7 = 31674ZS 8 = 883011SO 9 = 166037352UR 10 = 434782608W...
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6 votes
2 answers
702 views

Compact mathematical expression [closed]

Make a mathematical expression whose value is equal to 2 that uses all the digits 0, 1, 2, ... 9 exactly once and uses as few other mathematical symbols as possible.
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4 votes
3 answers
3k views

Some doctors and a lot of hand shakes

At a congress there are some doctors, and everyone shakes a certain number of hands (never more than once with the same person). The doctors can be divided in two groups: -Group O: the doctors who ...
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  • 325
0 votes
1 answer
95 views

How many colleagues went to Starbucks?

You go to Starbucks with some colleagues, everybody gets a cappuccino. Every cappuccino contains only coffee and milk (at least some coffee and some milk) and no other ingredients, but everyone has a ...
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  • 325
12 votes
1 answer
1k views

Patrick and Rachel go to a tennis tournament with 7 other couples

Patrick and Rachel go to a tennis tournament with 7 other couples. Each round is a single's match (1 vs 1). Nobody plays against his/her partner and nobody plays twice against the same player. At the ...
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  • 325
3 votes
2 answers
146 views

Productive Neighbours

Seven tiles need to be placed so that one is placed in each of the curved "regions" formed by the three circles. One tile has been placed for you. Each circle has a corresponding statement. ...
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6 votes
1 answer
301 views

Problem XXX (Squared) - Number Stile

Happy weekend folks, The intersections of the three circles divide their interiors into seven "regions" By complete non-coincidence, we have seven tiles A "valid" placement is one ...
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2 votes
1 answer
100 views

How to fill up the numbers in a set of empty discs drawing a pentagon? The target sum is 10 [duplicate]

Can anyone explain to me the math behind the problem? I want to convert the mathematical solution into an efficient algorithm. The target sum can be any given number. For reference please check the ...
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-2 votes
1 answer
199 views

Summa Cum Laude - Tile and Error

For any set X, {X} denotes the sum of its elements. "I divide {A}" means all items in that set are divisors of the sum of A's elements. Arrange the tiles so that four are in each set and the ...
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0 votes
4 answers
178 views

Solve for 69 using only 1 9 9 2 in that order [closed]

You must use all the digits of $1 9 9 2$ in that order to come up with $69$ as the answer. For example $ - (1 + \sqrt {9})! + 92 = 68 $ but you must solve for $69$.
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2 votes
2 answers
155 views

Twenty (or fewer) questions to solve a three-digit code

In an episode of Odd Squad, the squad are left with five yes/no questions to get a three digit code out of a villain. Luckily for them, they have sufficient questions to guess the first number by ...
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5 votes
2 answers
367 views

Determine the highest possible sum of all faces of cube

There is a non-negative integer written on all six faces of a cube. Integers on all possible three common adjacent faces (all faces are adjacent to each other) are multiplied and then they are added. ...
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  • 1,085
13 votes
2 answers
739 views

Only one such number exists

A 5 digit number ABCDE is divided by 2,3,4,5,6 and gives A,B,C,D,E as the remainders respectively. Can you find the only possible number? This was asked in my math exam, I think it would make a good ...
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  • 1,085
18 votes
3 answers
1k views

Strategic betting on the world series

Your wealthy father-in-law gives you \$10000 to place a "double-or-nothing" bet on Boston Red Sox in the World Series [1]. In other words, your father-in-law expects to receive \$20000 if ...
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2 votes
1 answer
170 views

A number of ten different digits, divisible by 8, 9, 10, and 11

Each of the digits 0 through 9 is used exactly once to create a ten-digit integer. Find the greatest ten-digit number which uses each digit once and is divisible by 8, 9, 10, and 11.
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-5 votes
1 answer
147 views

The peculiar inequality

Let's have the following relation $\sqrt[3]{\frac{(x+1)^3+x^3}{2}}\lessgtr\frac{2x^2+2x+1}{2x+1}$ where $x$ a positive integer greater than zero. Which inequality is valid?
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1 vote
1 answer
140 views

Zettler's Encyclopedia

On epiphany 1735, Sir Zettler, who was a great publisher from the old continent, promised to issue a "Great Universal Encyclopedia of Collectible Wisdom". It was meant to be affordable for ...
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6 votes
0 answers
273 views

Turn the dials until each of the 12 columns add up to 42

I received the wooden puzzle below for Christmas. After playing with it for a while I decided I needed to actually write something down if I was going to solve it. Eventually I just wrote an algorithm ...
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  • 161
-4 votes
1 answer
125 views

Quantity expressed as the difference of two squares

What is the trick you need to use to be able to express the quantity $(4x^4+8x^3+7x^2+3x+\frac{1}{2})$ as the difference of two squares? addendum: The answer contains only rational numbers greater ...
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-5 votes
3 answers
139 views

What is the Result of this icon Equation? [closed]

from:https://www.rondogo.sk/hra I have problem with heart :) A) 19 B) 20 C) 21 D) 22
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-1 votes
2 answers
118 views

What is the right number to replace and why?

Can anyone help me solve these puzzles? Puzzle from: www.treningmozga.com
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  • 11
4 votes
3 answers
932 views

Finding a Kakuro trick

The following screenshot is taken from the Android app Kakuro++ (level 9 riddle 12) And I verified the current status within the app. I managed to solve the puzzle by guessing a 50/50-number and ...
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2 votes
1 answer
267 views

What number is missing in the pentagon? [closed]

What number is missing in the pentagon? Puzzle from: https://www.rondogo.sk/hra/
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1 vote
1 answer
97 views

Equal row-products and column-products in a given array [closed]

I don't know if this is the right place to ask this question, but I'm stuck on this and can't figure out how to even proceed. Any hints anyone? Is it possible in a 5 × 5 array of integers for all row ...
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1 vote
1 answer
158 views

Math riddle puzzle

I stumbled upon this math puzzle over one android app. You need to find the unknown number in the puzzle. 92 = 725 61 = 215 74 = 327 52 = ? According to the author ...
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  • 13
2 votes
3 answers
253 views

Reversible number problem

These are the reversible numbers In this example we have an operation that on one side gives the result 6 and turning it gives it 12. Is it possible using reversible numbers and mathematical ...
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2 votes
2 answers
373 views

Minimum number of questions?

This is an interesting puzzle which I've been racking my brain to solve for some time. I've found different variations of this puzzle but it does not seem like this one has been asked before. Here it ...
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3 votes
0 answers
273 views

What's the missing number in this 3x4 matrix? [closed]

$$ \begin{matrix} 3 & 3 & 5 & 6 \\ 2 & 3 & 6 & 1 \\ 7 & 6 & 3 & x \\ \end{matrix} $$ This math puzzle is supposed to be solved by middle school ...
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3 votes
0 answers
263 views

Find a missing number in this 28x21 grid

355|066|677|855|677|081|044|855|355|062|216|677|216|855|224|044|034|046|051|677|355|264|044|046|044|351|886|043 043|044|886|357|886|352|225|357|043|222|993|001|233|968|046|225|062|041|351|886|043|227|...
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6 votes
2 answers
2k views

Math puzzle: I know the answer, what is the equation? Use all digits 1-9

A few years ago, my child brought a puzzle home from their 6th-grade math teacher. The solution was to use all the numbers $1−9$ only once and make the equation true. Using a spreadsheet, I was able ...
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2 votes
1 answer
193 views

Fill each blank with a digit 1-9 without any repetition [closed]

Fill the following place holders with digits in the range from 1 to 9. Each digit only appears once and make the equation sum up to 100. _ /_ * _ + _ * _ * _ / _ + _ * _ = 100 Also, what is the ...
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  • 39
-5 votes
1 answer
108 views

Number puzzle: 5+3=28 [closed]

Another puzzle to solve! :) $5+3=28$ $3-1=24$ $7+3=?$
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-4 votes
1 answer
109 views

Clock puzzle - 17:45 + 22:05 = 1510 [closed]

I have designed this clock puzzle for you to solve! $17:45 + 22:05 = 1510$ $20:55 - 17:30 = 35$ $06:40 * 19:20 = ?$
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5 votes
1 answer
145 views

The digits of the cube of a 3-digit number X

The digits of the cube of a certain 3-digit number X are, from left to right, the square of a 2-digit number, followed by the square of another 2-digit number, followed by one digit. (Everything is ...
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0 votes
2 answers
115 views

Which number replaces the question mark?

I'm trying to solve puzzles to exercise my brain. I'm stuck on this test, I printed it from Mensa IQ Test, an app on Android store. Can someone help me? Below is the test:
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  • 103
-8 votes
1 answer
135 views

Puzzling rectangles [closed]

Can you find two unequal rectangles whose areas add to $5\sqrt5$? No computer solutions please.
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15 votes
3 answers
1k views

A Perfect Diamond of Numbers

A diamond of numbers is an arrangement of circles in the shape of a trapezoid (see figure) in which the number in any circle above its central (longest) row is the sum of the two numbers in the ...
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31 votes
2 answers
3k views

Sum of the first 86 square roots

Without using a calculator or a computer, can you compute the sum of square roots of the first 86 natural numbers, rounded to the nearest integer? In other words, we are looking for $\sqrt{1} + \sqrt{...
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3 votes
1 answer
260 views

Six single-digit numbers surrounding a three digit number - what's the rule?

Source: SOF World IMO Class 9 Find the missing number, if the same rule is followed in all the three figures. 2 1 4 2 3 3 4 6 7 \ | / \ | / \ | / 693 374 ? / | \ / | \ /...
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9 votes
2 answers
364 views

Climbing scoring puzzle inspired by today's olympic event

Necessary information. The sport climbing consists of three disciplines: speed climbing, bouldering, and lead climbing. In combined events, the disciplines come in this order, and the combined score ...
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  • 223
-2 votes
2 answers
165 views

How to solve this problem on overlapping?

In cases of problems involving order and ranking where there are two indices (namely left and right) there is a particular chance of overlapping. Let us take an example to justify this: Ranjan is ...
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1 vote
1 answer
191 views

Puzzle storm to infinity

I have been playing Puzzle Storm on Lichess lately. Essentially it involves solving chess puzzles within a given time limit. Additionally, the player gets a time bonus for a certain number of moves. ...
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  • 21
5 votes
1 answer
157 views

Sum and product of 9 digits

Adding single digits 1 to 9, the result is 45 and their product is 362880. Are there any other 9 single digits with sum 45 and product 362880?
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3 votes
0 answers
115 views

Expected waiting time [closed]

You arrive at a station at time t=0. Train A can come anytime between [0,5] and train B can come anytime between [0,7] and train C can come anytime between [0,9]. You will board the first train you ...
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-1 votes
1 answer
257 views

Grandfather and Grandson

My Puzzle is as follows- Once, I said to my friend that, "In 1932 I was as old as the last two digits of my birth year. When I mentioned this interesting coincidence to my grandfather, he ...
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