Questions tagged [calculation-puzzle]

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

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15
votes
1answer
1k views

Rybo switched the calculator keys!

I'm Dave. In revenge for my calculator key-switching prank, Rybo has performed a similar prank on me! My calculator has the usual number keys, and keys for the usual four arithmetic operations: ...
13
votes
5answers
675 views

Labelling a Snow Flake Graph to Attain Minimum Sum

Label the vertices (or nodes) of this graph with positive integers so that any two nodes are joined by a edge (or line) if and only if the corresponding integers have a common divisor greater than 1 (...
7
votes
2answers
393 views

Fuzzy the Fuzzball

Fuzzy the fuzzball was very sad. He had lost his fuzz. Everyone knew if you lost your Fuzz you could no longer be a fuzzball. Fuzzy went to this friend Frizzy and shared his dilemma. "Don't worry, ...
7
votes
4answers
646 views

Paint the rectangle with least movement

There is a painting brush tool that can paint a circle area of $1$ unit radius. What is the shortest paint track for painting at least a $100*100$ units rectangle area on wall? How much did the brush ...
7
votes
1answer
735 views

MC Frontalot 80085

MC Frontalot is a musician, and one of his songs is a word problem that seems to me like it belongs here. If you want to listen to it instead of just reading the lyrics, a quick video search of "MC ...
7
votes
4answers
2k views

A truly amazing way of making every possible positive integer

This is a follow-up to "A truly amazing way of making the number 2016": For every positive integer $n$, find a mathematical expression that yields the value $n$ while obeying the following rules:...
7
votes
1answer
1k 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 ...
6
votes
2answers
204 views

Use all of the following symbols and numbers in one equation

Use all of the following symbols and numbers in one equation for the result to be equal to 10 (14, 12, 9 , 7, 3) (÷ × - ÷)
4
votes
4answers
582 views

Twos For Thought

How many twos do you need to get to the number $100$ exactly? Example: $22+22+22+22+2^2+2^2+2^2$ This example method uses 14 twos and is obviously not ideal. Can you find a way that uses the least ...
4
votes
3answers
2k views

The bird and the train

This question is one I found in a competitive exam paper, and has two solutions: one simple and one complex. A train starts from the east end of a 200 km long east-west track at 50 km/h. At the same ...
4
votes
1answer
252 views

The Autonumerigram Challenge [duplicate]

Some phrases both refer to a number, n, and are comprised of n alphabetic characters. I call any such phrase an autonumerigram. For example, four has 4 letters seven plus seven has 14 letters ...
1
vote
7answers
892 views

Correct way to add 22 to 4 to get 70

Based on the other "Correct way to add 22 to 4" puzzles. Tell me the correct way to add 22 to 4 to get 70 As in the other puzzles, all numbers are in Base 10.
-3
votes
1answer
2k views

Number of days to fill the Lake with 1/32th part

There is a lake in which every day some new lotus flowers grow. Their growth follows a pattern; if on a given day there are X flowers, then on the next day there will be 2X flowers will be there. So ...
-7
votes
2answers
315 views

Burger and chips calculation puzzle 2 [closed]

This is easy though I think it is very fun to think about! S+S+S=30 S+H+H=20 H+F+F=9 H+F*S=?
78
votes
15answers
15k views

Making π from 1 2 3 4 5 6 7 8 9 [closed]

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 3 ...
29
votes
4answers
46k views

Create all numbers from 0-100 only using all of 1,2,3,4 and 5

Create all numbers from 0-100 only using 1,2,3,4 and 5. No repeats and you have to use each number. Also, you can use any operation. I've only gotten to 50 by pure brute force. I think that this might ...
18
votes
16answers
6k views

You're invited! Now what?

(semi-interactive puzzle) BRIIING! BRIIING! BRIIING! You wake up with a start. It's 6:30... already!? Darn. You roll slowly out of bed, preparing for the day ...
61
votes
12answers
22k views

XOR - Is it possible to get a, b, c from a⊕b, b⊕c, a⊕c?

Just got a simple question from a friend; still thinking. Let's share it! Is it possible to get a, b, c when you have a⊕b, b⊕c, a⊕c ? where ⊕ is the boolean ...
26
votes
6answers
29k views

The 10,958 Problem

Here is the task: Write down 10958 using all 1-9 digits in ascending order and only one time. You are allowed to: 1) group digits into numbers 2) use 5 basic operations: + - * / ^ ("^" ...
33
votes
2answers
2k views

A moderate visual number puzzle

In the following diagram, each red dot represents a positive number. The dot-numbers on each of the five circles spell out either a word (each dot corresponding to a letter) or a number (each dot ...
17
votes
2answers
1k views

Logically linked numbers

The left and right numbers are linked. What should the last number on the right be, and why? \begin{align} 135759&: 1 \\ 151364&: 4 \\ 255075&: 9 \\ 279422&: 36 \\ 292620&: 91 \\ ...
21
votes
6answers
8k views

3x3 "Magic Square" of Prime Numbers

During the thinking and analysis of some mathematical problems, I came up with this puzzle: Just like any magic square, one has to fill in $9$ different numbers $P_1, P_2, \dots P_9$ to a $3 \times 3$...
28
votes
3answers
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 ...
33
votes
2answers
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 ...
31
votes
1answer
2k views

What is a BEN Number™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with Number version puzzles. If a number conforms to a special rule, I call it a BEN Number™. Use the following examples ...
26
votes
3answers
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 $28x+30y+31z=3650$?
16
votes
5answers
961 views

4 Gridded Prime Numbers

You have the first four prime numbers ($2$,$3$,$5$ and $7$) which are gridded and shown as below: You are trying to get highest total score you can reach with arranging the numbers by rotating (no ...
16
votes
4answers
3k views

How many smurfs are there?

Papa Smurf gathered some berries from the forest to the village and smurfs ate all those berries: The smurf who ate the most actually ate one-fourth of the berries eaten by the rest of the smurfs. ...
12
votes
2answers
962 views

Ernie and the unfair division of the dessert

I was pleased to get an invitation to Ernie's place for dinner last Wednesday. The triplets were staying for the week so I knew Ernie would be making an extra effort to cook a gourmet home-cooked ...
2
votes
5answers
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, ...
19
votes
17answers
10k views

Number 88 from the digits 2, 0, 1 and 7?

Can you use the digits 2, 0, 1 and 7 each only once to create the number 88?
14
votes
8answers
4k views

How to get 32 by using +1 , +1 , ×3 , ×3 , ÷2 , ÷2, ^2, ^2?

How to get 32 by using +1,+1,×3,×3,÷2,÷2,^2,^2? (The last two operators are 'squaring'.)
6
votes
5answers
2k views

Simple Math Problem #2

Link to previous puzzle Simple Math Problem #1 (not linked to this one) Here is another simple math problem. Can you solve it? Examples: $25 + 12 = 33$ $37 + 13 = 44$ $40 + 24 = 66$ $64 + 26 = 88$ ...
4
votes
0answers
796 views

Number Sequence Series-Question 7

This is a series of questions that are created by me. Here is question 7: (23),(55),(155),(1255),?,?,(56139611) I will give a hint to you guys in one month if nobody can solve it.
33
votes
1answer
1k views

Integers around a circle with consecutive pairs adding to a square

The integers 1 to 50 are placed around a circle in such a way that the sum of any two of them which are adjacent is a perfect square. Of these integers, the even numbers are then removed. Restore them....
31
votes
1answer
2k views

Computation without a computer

In the number $(1+\sqrt{3})^{2015}$, what is the 224th digit after the decimal point? You may NOT use a calculator, computer, or any electronic aid to answer this question. Only pen(cil), paper, and ...
19
votes
1answer
1k views

Ernie and the Cake Cutting

Ernie had spent most of the afternoon at my place, helping me with the tile grouting in my new bathroom. It had been a difficult and messy job, so when he asked if I could do him a "small favour" I ...
16
votes
3answers
579 views

Word Number Puzzle

If letters are factors of equations: zero = 0 one = 1 two = 2 three = 3 four = 4 five = 5 six = 6 seven = 7 eight = 8 nine = 9 ten = 10 twelve = 12 fifteen = 15 twenty = 20 thirty = 30 ...
9
votes
1answer
420 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 ...
8
votes
3answers
8k 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 ...
8
votes
1answer
409 views

Whose birthday is it?

A group of people have gathered for a birthday celebration. Their ages are related as follows: The product of the 1st person's and the 2nd person's ages is $311\frac{2}{3}$ plus the 3rd person's age. ...
8
votes
2answers
447 views

A sequence defined by a single fraction

I have a sequence of numbers here, which follow a very simple rule that can be expressed using a single fraction: 1, 2, 10, 11, 13, 15, 20, 22, 25, 28, ... What is this rule (in particular, what ...
8
votes
2answers
729 views

Four Magic Ellipses

These four ellipses represent four sets and all the possible ways they can intersect (a Venn diagram, in other words). There are 8 regions inside each ellipse, and 15 regions altogether. Is it ...
2
votes
1answer
196 views

Number Sequence Series-Question 3

I want to share a series of questions that are created by myself. I will give a hint in 24 hours and my answer in 3 days given that nobody could answer my question. Here is my number sequence: 2020,...
32
votes
4answers
2k views

Sum other numbers

Begin with a flagrantly erroneous summation and a woefully vacant substitution table. 234 + 5 Digit 2 3 4 5 6 7 8 ------- ...
18
votes
4answers
3k views

I don't want the smallest one, I want the second-smallest one

Inspired by my struggles with a certain open-source online learning platform's grading system: You are working in a computer language with a limited set of built-in functions. You have a set of $m$ ...
15
votes
2answers
968 views

Buttons on an old non-scientific calculator are less sensitive

All 5 numbers are entered in an ascending order. These numbers are in an arithmetic progression. The value of the fifth number, i.e. the largest number, is less than 99. While adding these ...
15
votes
7answers
4k views

Find out the number using three clues

I was asked this question about finding a number and three clues were given which are as follows. If this number is multiple of 5, it would lie between 1 to 19. If this number is not multiple of 8, ...
13
votes
1answer
964 views

Ernie and the Bubbles of Lucretia

"So, what do you know about milking spiders?", asked Ernie as he passed a fresh cup of coffee to me. Good grief!, I thought and gave an involuntary shudder as I glanced at the milk jug sitting ...
11
votes
10answers
895 views

Four fours to get $\pi$ [closed]

Four fours is a famous puzzle (made trivial with logarithms). For this puzzle, we take inspiration from Glen O's challenge from a few years back. The rules here are slightly different, but the goal is ...