Questions tagged [arithmetic]

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

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8
votes
1answer
429 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)....
8
votes
2answers
335 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 ...
2
votes
2answers
177 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 ...
10
votes
4answers
746 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 ...
14
votes
1answer
613 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 ...
5
votes
2answers
179 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 ...
40
votes
7answers
6k views

9-5=5? Matchstick problem

Move one matchstick to make an equality. Question made by me (Is this too easy?)
7
votes
2answers
676 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 ...
25
votes
6answers
1k views

Some numbers are more equivalent than others

[Second part and bounty challenge appended in May 2020]           ALL ANIMALS ARE EQUAL    BUT ...
4
votes
1answer
122 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 ...
9
votes
7answers
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 ...
4
votes
3answers
185 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 ...
11
votes
2answers
303 views

Find the missing number from the pyramid

? 1 3 3 3 9 9 3 1 9 Find the missing number in the pyramid?
1
vote
0answers
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) (÷ × - +)
1
vote
1answer
142 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 ...
2
votes
2answers
173 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 ...
1
vote
0answers
88 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?
4
votes
1answer
4k views

Help solving a math puzzle table

I am struggling to find the answer. Here is the source: math logic puzzle phone app.
-2
votes
2answers
317 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. ...
-4
votes
3answers
3k views

Brain Testing Logical Reasoning Puzzle

Can you answer this logical puzzle? Puzzle Source: https://www.funwithpuzzles.com/2018/12/brain-testing-logical-reasoning-puzzle.html
4
votes
2answers
231 views
3
votes
10answers
18k views

Make numbers 1-30 using 2, 0, 1, 9

This is very similar to the 2, 0, 1, 8 problem. Just try to make all numbers 1-30 using the digits 2, 0, 1, 9. Rules: Use all four digits exactly once Allowed operations: +, -, x, ÷, ! (factorial), ...
11
votes
1answer
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 ...
3
votes
2answers
265 views

Missing numbers

The hexagon below is almost complete but there are 3 missing numbers. Try replace the question marks! Hint Hint2: Hint3
10
votes
1answer
290 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 ...
16
votes
2answers
638 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 ...
11
votes
1answer
229 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 ...
7
votes
3answers
715 views

What is a Trio 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 Trio Word™. Use the ...
0
votes
2answers
269 views

Find the number that does not fit into the pattern shown below

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 12 34 56 78 910 1112 1314 1516 1718 1920 2122 2324 2526 2728 2930 3132 3334 3536 Each row forms a set which implements a pattern. The two patterns ...
18
votes
5answers
1k views

Primes less than 100 in a 4 x 4 board

Place one of the digits (0 to 9) in each of the cells of a 4 x 4 board so that as many as possible of the 25 primes less than 100 divide at least one of the 10 positive 4-digit numbers that can be ...
13
votes
2answers
286 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 ...
1
vote
3answers
357 views

Please help me to identify the pattern

$(A)72$ $(B)18$ $(C)9$ $(D)19$ 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 ...
4
votes
1answer
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 ...
7
votes
6answers
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 ...
-4
votes
1answer
221 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
9
votes
6answers
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 = ...
1
vote
2answers
159 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 (...
0
votes
1answer
118 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 \...
-2
votes
1answer
240 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/...
6
votes
3answers
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.
4
votes
2answers
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 ...
10
votes
1answer
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 ...
30
votes
1answer
1k 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 ...
12
votes
1answer
482 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 ...
10
votes
2answers
598 views

A Magic Flying Saucer

Place 19 different positive integers on the vertices of this graph so that the 13 products of three numbers in a straight line are all equal. Do so in such a way that the product is as small as ...
3
votes
2answers
184 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 ...
7
votes
2answers
934 views

What is a Finale 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 Finale Number™. Use the following examples ...
37
votes
4answers
5k views

Find average age without revealing your age

Ana, Barbara, Carol and Diana want to know their average age. But no lady wants to disclose her age. They decide a strategy and use a calculator (one that doesn't store steps) and tapped some keys ...
7
votes
2answers
949 views

Big number puzzle

I saw this on rec.puzzles many years ago, but can't find the reference to credit the source. I am thinking of a large number. If you want to multiply it by a two digit number $ab$ with $a \lt b$, ...
8
votes
2answers
265 views

What is a Valid 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 Valid Word™. Use the ...