# Questions tagged [calculation-puzzle]

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

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### Scrap puzzle to count how many

There are 250 scraps. For each 11 removed, one extra can be obtained. How much maximum is possible, if one cut by one unit? I have read this somewhere, and one guy gave the answer as 25, but I can't ...
1k views

### Working schedule (with explanation) [closed]

Alice, Bob, Chris, Dave, Eric, Fred and Laura used to work in a restaurant 6 days a week, from Tuesday to Sunday (Monday is a day off). Every one works at least for one day, and at least two people ...
854 views

### The Wizard's Gambit

An evil wizard has captured and thrown you into a dungeon. This is not a normal dungeon though. It's magical. Each room has an associated "level" and 9 doors. The first door can be used to go to ...
252 views

### Calculate RPM ratio A to D? [closed]

According to the picture: cogwheels A and D have 60 jags each, cogwheel B has 40 jags, and cogwheel C has 20 jags. If cogwheel B turns at 20 RPM, calculate the ratio of A's speed in RPM to D's.
11k views

### Can you solve this math problem

If these are true : 5 + 3 = 158 9 + 1 = 910 8 + 6 = 4814 4 + 4 = 168 then 7 + 3 = ??
3k views

### In a certain language if the word STABILIZE is coded as JHXDJQSYA, then how is the word RESPONSES coded in that language?

In a certain language if the word STABILIZE is coded as JHXDJQSYA, then how is the word RESPONSES coded in that language? LRCRPOQDP PDQOPLRCR LRCRPPDQO LQCRPPDQO LRCRPPDOQ I tried it ...
3k views

### Five loaves and the extra traveller

Two people are travelling together. One of them has three loaves of bread; the other one has two. At some point they stop to eat lunch. A third traveler that happens to walk by joins them. They split ...
2k views

### Is my bank going to be bankrupt?

Today I heard a rumor that my bank will go bankrupt soon. So I went to my bank, and indeed I found out that they have introduced some weird new rules that clearly indicate that there is something ...
830 views

### Dragon lizards in Hogwarts

Albus Dumbledore keeps 274 dragon lizards in his terrarium in Hogwarts. One day he removes two thirds of the male lizards from the terrarium; it is easy for him to tell the males apart from the ...
692 views

Start with an unlucky Friday number. Multiply by the gables on Hawthorne's house. Add the number that a stitch in time saves. Add the number of blind mice. Subtract the number of William Pene du Bois' ...
709 views

### Time teaser - clock losing time [closed]

I recall a question that went like this: If a clock is at noon on Sunday, and the clock loses 9 minutes per hour, what time will the clock next show the correct time? How do you work that one out?? ...
5k views

### My grandfather's socks

My grandfather has a big drawer where he keeps his socks. The drawer contains more than 900 but less than 1000 individual socks. Each of his socks is black or blue, and there are more blue socks than ...
194 views

### Shifting the stack as it is

There are $3$ saucers. And there are $5$ disks, say A,B,C,D,E, having respective areas $1,2,3,4,5$. That is, E is the largest disk and A is the smallest one. They are placed in the order E,D,C,B,A in ...
11k views

### What's your price for the eggs? [closed]

I came across this problem some years ago in a book (which I won't mention, and request others to not mention if they know). The solution is quite elegant and difficult to arrive at by mere trial and ...
3k views

### Filling up 100 coins in 10 bags

There's a king who wants to appoint a new minister. To check the intelligence of the interested men, he gives the following problem: There are 10 bags and there are 100 coins. You have to fill all ...
2k views

### A puzzle about baking 88 pies

You surely remember that one of my grandmothers really hates mathematics (How do I convince my grandmother?). Yesterday I visited my other grandmother who really loves mathematics. She was in the ...
874 views

### How many GREEN coats?

Yesterday at our local highschool there were 29 pupils wearing BLACK coats 27 wearing RED coats, and 40 wearing BLUE coats. How many pupils were wearing GREEN coats?
471 views

### Bumblebees and Honey bees

The current market price of 175 honey bees is more than the price of 125 bumblebees, but less than the price of 126 bumblebees. Is it possible to buy 3 honey bees and 1 bumblebee for altogether at ...
5k views

### How do I convince my grandmother?

How do I convince my grandmother (who really hates mathematics) that there exist three positive integers $x,y,z$ that satisfy the equation $28x+30y+31z=3650$?
23k views

### Find length, width and height of a cuboid [closed]

Consider a cuboid (that is, a rectangular box / rectangular parallelepiped) with the following properties: the area of its top face is $240$ cm$^2$ the area of its front face is $300$ cm$^2$ the ...
490 views

### Quick and dirty: painting a fence

There are four fences, which are geometrical identical (same heigth and same length). The following four people need the specified time to paint it: Bob needs 2 hours. Simon needs 3 hours. Tommy ...
975 views

### Probability of Seeing a Car in 10 Minutes & 30 Minutes [closed]

On a deserted road, the probability of observing a car during a thirty-minute period is 95%. What is the chance of observing a car in a ten-minute period? Hint: To clarify the question we are saying ...
6k views

### Aeroplane roundtrip in the wind

If an aeroplane makes a round trip and a wind is blowing, is the trip time shorter, longer or the same as without wind? Why? Round trip mean aeroplane go from point A to point B and then return to ...
3k views

### Product and Sum

My fellow mathematicians Paul and Sam are very fond of mathematical puzzles. One day, I came up with the idea on mathematical puzzles while three of us having lunch together. I: Hey, guys. I am ...
2k views

### 180 degree rotation matchstick equality

Several matchstick digits are still digits when rotated by 180 degrees: Note that 2 is rotated to 2. Thus, we can make a matchstick arithmetic expression which is valid when rotated 180 degrees. For ...
2k views

### whats the Missing Number?

In this grid of numbers, what is the missing number (in place of the question mark)? \begin{array}{|c|c|}\hline2&7\\\hline8&9\\\hline\end{array} \begin{array}{|c|c|}\hline0&3\\\hline5&...
3k views

### The story of green apples and red herrings

Let's say we are in a magic land with lots of fantastical animals and plants and whatever... Imagine you have way too much time, really like apples and love collecting and growing them. In fact, ...
4k views

### make a green profit in roulette

Story You meet a rich drunk CEO at a roulette table in Vegas. She explains to you that she has a way of almost guaranteeing a profit at this game by betting on only black. In the process she gets ...
734 views

### Can the car or the bike travel further?

There is a car and a motor-bike. The car and the bike both have an spare tire. Now, the car has a total of 5 tyres (one spare tire included) and the bike has a total of 3 tires (one spare tire ...
959 views

### The lights in the hotel

A hotel has $n$ rooms, numbered 1, 2, 3, etc. until $n$. At the hotel reception there are $n$ buttons, one for each room, also numbered 1, 2, 3, ..., $n$. Button 1 switches the light from on to off or ...
2k views

### Number Series - 1,20,171

$1,20,171,?,9625,57756,288775$ Please find the missing number in the series. I have already tried with squares, cubes and progressions but couldn't find the problem.
2k views

### Replace all letters with a digit and solve the equations

There are ten expressions written in the scheme below from left to right and top to bottom. Replace all of the ten distinct letters in the scheme with a single digit between 0 and 9 and make the ...
1k views

### Need help solving this code puzzle. Possible binary?

Me and a friend are trying to solve a series of puzzles, and this is the last one I need to solve and I'm stumped. It's a Christmas themed puzzle titled 'bLitZEN'. The only hints given are that the ...
3k views

### Ernie and the Alchemist's Gift

For Ernie, the task of choosing Christmas presents for his friends is always a struggle. I think that is because, while he finds it easy to solve problems relating to machines, mathematics, and ...
656 views

### Find the longest arithmetic expression with value equal to number of letters in its english representation

The expression twenty minus five has 15 letters (we ignore spaces) and also has the arithmetic value of 15. You can use standard math constants, operators and ...
652 views

### Lining Up Recruits

The good soldier Schweik had been ordered to line up a band of new recruits before their officer gave them a speech. The desired line sought to minimize the average difference in height of adjacent ...
1k views

### Ernie and the Drill Test

I dropped in to Ernie's place a while back and he asked me to stay and help calibrate his new Drilling Device. It was an impressive looking machine consisting of a large raygun-like thing mounted on ...
227 views

### Not your regular Caesar Cipher$\ldots$

What in the name of the USSR does this mean?! 59 103 106 138 -1 106 138 -1 81 -1 135 81 141 103 94 135 -1 106 122 141 94 135 94 138 141 106 122 100 -1 87 125 91 94 -2 -1 91 125 122 -3 141 -1 157 ...
2k views

### Sequence Brain Teaser: Fill the gaps to create arithmetic sequences

Fill in each blank unshaded cell in the diagram below with a positive integer less than 100, such that every consecutive group of unshaded cells within a row or column is an arithmetic sequence. This ...
3k views

### What, the answer isn't the No of the Yes is?

Doorknob knows exactly how to solve this, so I ask him to not answer this question. Well, here's the puzzle: No, an answer is the cube without A, No? The Yes is No. The squared answer, Yes, is to an ...
743 views

### How can we compute the 6 missing numbers?

There are 3 datatables. We forgot the numbers around the third square. How can we compute the 6 missing numbers?(there are question marks instead of them)
668 views

### Find out which instruction is wrong

The object of the following flow-chart is to rearrange the numbers in boxes 1, 2 and 3 in such a fashion that, at the end: ...
1k views

### Sell the fuel and become a Millionaire [duplicate]

You are living in the 22nd century. The fuel prices are unimaginably high and it is very rare to get, so the Government has introduced some new laws to control fuel smuggling. Rule 1: One cannot ...
231 views

### The hour glasses! [duplicate]

You have two hour glasses: A seven minute one and an 11 minute one. Using just these two hour glasses, accurately time 15 minutes.
363 views

### Wine with dinner

On a certain road there are 32 houses in a row, numbered 1 through 32, each inhabited by a single person. During the month of January each house is hosting a dinner date. House 1 on January 1, house ...
918 views

### Determine the Maths Function [closed]

You found yourself in a weird room, there was no doors, but a limited computer with no internet that has open an app that is displaying the following message: f(0) = 0f(1) = 549f(2) = 646f(10) = ...
279 views

### Determinine the delay on a phone call

Alice and Bob are telecommunicating in some way. When Alice speaks, it takes A seconds to reach Bob. When Bob speaks, it takes B seconds to reach Alice. Both Alice and Bob have clocks that tick at the ...
2k views

### Defuse the bomb, Mr. Rossi!

This is a very hot summer in Rome and you don't know what to do. You are the best detective in town but no crime seems to happen. You are all the day in front of your PC trying to solve some puzzles ...
1k views

### Ernie and the Orthogonal Network

I dropped in on Ernie a while ago and he told me that there was "good news and bad news". I asked him to tell me about it and he explained as follows: "Remember my Casimir-effect electric motor and ...
4k views

### How to make 21?

How do you make $21$ from the numbers $1$, $5$, $6$, and $7$? You can use the operations of addition, subtraction, multiplication and division, as well as brackets. You must use each number exactly ...