# Questions tagged [arithmetic]

For puzzles involving addition, subtraction, multiplication, or division.

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39 views

### Second by Second, Digit by Digit [closed]

You are currently attending your one-hour-detention for skipping the class free time, which is the last five minutes of the day. What is ironic is that you skipped it to apply for a Computer Science ...
39 views

### The two brothers' ages dilemma [closed]

There are many variations of this riddle, I made up this one to make my point : Jim is 8 years old and his brother Daniel is twice older. When Jim will be 10 times older than now, how old will Daniel ...
57 views

### Sum with letters, find the values

In the following addition setup, each letter correspond to a unique digit. Find the different values of the letters. Requirement: r is not equal to 0. ...
401 views

### The art of computer programming

EDIT: I know we are not supposed to edit in new requirements after first posting but as far as I understand it this requirement is implicit in all questions here: Explain your answer! At least a ...
107 views

### XOR -Is it possible to prove that if A=C⊕B then B=C⊕A and C=A⊕B using Boolean algebra only? [closed]

If you write out the truth tables then it's pretty simple but I was wondering if there was a nicer proof using Boolean algebra only
2k views

### 77-digit number divisible by 7 with seven 7s

The smallest number divisible by 7 with seven 7s is trivially 7777777. Then, what is the greatest 77-digit number divisible by 7 which contains seven 7s?
94 views

### Robot's Step, Step, Sent Back!

So there is this robot. Its origin is at (0, 0), index 0. Each pair of coordinates will have same numbers for x and y. How the robot moves is this: ...
155 views

### How to get these outputs using these inputs?

Examples of inputs and outputs: Input: 3 7 20 Output: 1 Input: 17 2 1651 Output: 34 Input: 4 3 5 Output: 2 Input: 1000000000 1000000000 1000000007 Output: 49 Input: 27 37 100 Output: 99
163 views

-What is your password?- my niece asks me. -It is a four digit number. -I know that. -It is divisible by precisely three primes. -Tell me more. -It has at least one common divisor greater than 1 with ...
158 views

### How many steps for matchstick-Lychrel numbers?

The Lychrel number is famous in the recreational mathematics. The process about the Lychrel numbers reverses arrangement of the previous number. Mimicking Lychrel numbers, I would like to devise ...
345 views

### Remember the 60s? Far-out man!

Can you convert the following to my unusual currency? 1.25, 1.75, 2.75, 3.25 Having done that, can you explain why some people think the smallest of these is somehow the biggest - at least as far I'm ...
178 views

### What's one and one and one and one and [closed]

Good morning. Today I am going to test your mental arithmetic. To do so I shall ask you to give me the sum of a series of ones. I shall say One and one and one and one and one and one, etc. Of course ...
622 views

### The numbers on blackboard

The numbers $2020,2019,2018,...,1$ are written on the blackboard from left to right. John repeats the following process until there is only one number left: John chooses the first two numbers from ...
184 views

### Swapping the first and last digits of an integer

Take any n-digit integer (n > 1) and interchange its first and last digits. If neither of these is 0, and they are different, does it happen infinitely often that the resulting number is a multiple ...
444 views

### Pairs of Bogotá Numbers

A Bogotá number is a positive integer equal to some smaller number, or itself, times its digital product, i.e. the product of its digits. For example, 138 is a Bogotá number because 138 = 23 x (2 x 3)....
6k views

### 9-5=5? Matchstick problem

Move one matchstick to make an equality. Question made by me (Is this too easy?)
681 views

### A Covid-19 puzzle: Alcohol for your School!

You are the principal of a primary school in HK. Schools are resuming soon, and you have to ensure that your school have enough alcohol. Each of the 30 classrooms should have a bottle containing 500mL ...
124 views

### Numbers Relation Puzzle

I've written a numbers relation puzzle, I'd like to share it with you and see what you fellas think. ------ Try to find the relation between the numbers------ Good to know: there are 2 parameters ...
752 views

### Smallest integer whose first n multiples contain the digit 1

For some time now I have been investigating the function $M(n)$, the least integer such that the first $n$ multiples of $M(n)$ contain the digit $1$. Thus $M(3) = 51$, because $51$ is the smallest ...
1k views

### Confusion on a math puzzle

One of my colleagues asked me below puzzle, Three friends went to a picnic. 1st and 2nd friends collected woods for cooking where 3rd friend did not participated because he was sick. 1st friend ...
188 views

### The death prism

One day, you are caught by a evil wizard. He presents you with a prism, and says, "You can ask me to turn this prism to any $n$-angled right prism. Then you shall fill in $1$ to $3n$ with no ...
33 views

### Use all of the following symbols and numbers in one equation for the result to be equal to 10 [duplicate]

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

### Make the numbers 1-100 using 8 8s

Rules: Make the numbers 1-100 using eight 8s Use the operations + - * / exponentiation and ! No Rounding as in $(\sqrt{88}+8*8+8+8+8)/8= 12$ No using other digits Multi digit numbers ...
174 views

### Make the numbers 1-100 using six 6s

Rules: Make the numbers 1-100 using six 6s Use the operations + - * / exponentiation and ! No Rounding as in $((6 - (6 + 6) / 6) + 6!!) / 6 = 9$ No using other digits Multi digit ...
101 views

### What could be the answer of this maths puzzle? [closed]

Found this puzzle online. Tried many possible combinations of numbers with multiplication, addition etc. Has anyone ever solved this?
243 views

### NineFind - Which 9 Numbers Are Correct?

Text Version: ...
319 views

### Make the numbers 1-50 using the digits 2, 0, 2, 0

Try to make all the numbers from 1-50 using 2, 0, 2, 0 exactly once. Rules: Use only the operations +, -, *, /, !, exponents and square root No rounding eg. ...
447 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 ...
268 views

### Missing numbers

The hexagon below is almost complete but there are 3 missing numbers. Try replace the question marks! Hint Hint2: Hint3
333 views

### Find the missing number from the pyramid

? 1 3 3 3 9 9 3 1 9 Find the missing number in the pyramid?
293 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 ...
698 views

### This new puzzle type needs a name {5}

I believe I have invented a new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by solving the 9x9 sudoku; each of the 9 symbols ...
231 views

### One Step Forward, Two Steps Back

What is the next number in this never-ending sequence? 0 1 1 110 111 101 11000 11101 10101 1100110 1001011 ...
295 views

### Happy birthday Ramanujan!

On December 22 2019, Ramanujan would have been 132 years old. In his memory here are two puzzles around 132. In the six vertices of each of these graphs place six positive integers that add up to ...
98 views

### Highest scoring words based on distance travelled along the alphabet v2

This is a follow on from my previous word puzzle: Highest scoring words based on distance travelled along the alphabet The twist in this puzzle which opens it up a lot more is that the alphabet can ...
460 views

### Highest scoring words based on distance travelled along the alphabet

For any word we define it's alphabetic distance to be the total amount of places in the alphabet you need to traverse between each letter. Example: WORD has a score of 25 8 character distance ...
161 views

### Free Assignment: Longest Word Worth a Million

This is very much inspired by this question. Take the first 26 primes and relate each one to a letter of the alphabet. On this occasion, you may choose how each number is mapped to each letter (...
362 views

$(A)72$ $(B)18$ $(C)9$ $(D)19$ Source:My coaching DPP The question asks you identify the pattern and find the missing character. I have been trying to solve this problem from a long time but I ...
3k views

### Longest word worth at most a million

An old and popular puzzle, recently revived on Twitter by Alex Bellos, Chris Smith, and others, asks to take the first 26 primes, relate each to letters of the alphabet (A = 2, B = 3, C = 5, ..., Y = ...
223 views

### How do I solve this problem?

I am trying to answer this puzzle - which of the five potential answers is correct, and why? This test comes from Metropol iq1 book
122 views

### How do I solve this multiplication problem?

I am trying to answer this puzzle my friend created and sent to me - which of the five potential answers is correct, and why? \$ 10 \times 5 = 60 \\ 6 \times 12 = 72 \\ 8 \times 3 = 44 \\ 5 \...
248 views

### Missing Number Picture Puzzle

This is is logical reasoning puzzle in which your challenge is to find the relationship among the given numbers and then find the value of the missing number. Source: https://www.funwithpuzzles.com/...
647 views

### Number Equation Matrix

Can somebody please solve this? My daughter's school teacher gave her this puzzle to solve at home. But to me it seems a little out of order, and that's why I am asking here for help.
237 views

### Primes from arithmetic and geometric progressions

The five primes, 131, 157, 211, 349, 739, are neither in arithmetic or geometric progression, but are instead the sum of the corresponding terms of two progressions of five terms each, one arithmetic ...
268 views

### What is a Commutative Word™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles. If a word conforms to a special rule, I call it a Commutative Word™. Use ...
483 views

### What is a Heptagon 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 Heptagon Number™. Use the following ...
185 views

### Rearrange these 9 digits - combinatorics puzzle

4 3 2 7 1 9 6 5 8 Can you rearrange these 9 digits so that in all of the 8 directions the difference between one of the digits and the sum of the remaining two shall always be the same? In the ...
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 ...