Questions tagged [arithmetic]

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

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20
votes
2answers
773 views

Honeydripping around the clock

      What path could a honeybee follow, beginning and ending at top center, visiting every empty cell exactly once and dripping 2 drops of honey into the last cell? Start ...
10
votes
2answers
307 views

How to fill a honeymoon

        How can a honeybee visit all cells exactly once in this crescent shaped honeycomb, beginning at the bottom tip and ending at the top? The starting cell, at ...
9
votes
1answer
286 views

H-one-one-oneycomb

        What path could a honeybee follow to fill all cells with honey, beginning and ending at the center and visiting every cell exactly once? At first the only ...
3
votes
2answers
407 views

Get the largest number using the crazy circuit board

There is a crazy circuit board with three kinds of elements which can change the signal value. All intersecting paths are connected (but paths touching by a single point are disconnected). There is ...
3
votes
1answer
184 views

Arithmetic Puzzle

The British Independent and i newspapers run what they call an "Arithmetic Puzzle", which comprises a grid of nine cells, with each cell separated from the others by arithmetic symbols: (+ - / *), and ...
-6
votes
3answers
609 views

A (Simple) Arithmetic puzzle

I'm hoping this one was not posted here already, tried to search a bit and didn't find it. It's a really nice brain teaser: Add arithmetic operators (plus, minus, times, divide) to make the ...
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 ...
2
votes
2answers
334 views

It is related to a type of mathematics game

Start with two digits from $1\dots9$ to form a $2$-digit number. Multiply this number by a single digit from $1\dots9$. Add the result to another two digit number from $1\dots9$, and calculate the ...
6
votes
2answers
1k views

Difficult sequence

Here I go : $3 + 5 + 6 = 15 \ 18 \ 72$ $5+ 5 + 6 = 25 \ 30 \ 94$ $5 + 6 + 7 = 30 \ 35 \ 85$ $5 + 5 + 3 = 25 \ 15 \ 73$ $9 + 4 + 7 = 36 \ 63 \ ? $ Replace ? with appropriate number
5
votes
4answers
982 views

How old was Matthew when his brother died?

When Sam's father died, Sam's uncle, Matthew (his fathers only brother) was twice the age of Sam minus 14 years. As Sam and Matthew grew older they became friends. When the younger of the two turned ...
6
votes
1answer
156 views

Age of Samantha and her grandchildren

Samantha is suffering from Alzheimer's and uses math to help remember things. Samantha has two grandchildren. Samantha youngest grandchild's age when raised to the power of the square root of her ...
-3
votes
1answer
228 views

In which year(s) could I have been born, if you know my unexact age in an unexactly dated source (unexact means exact up untill years) [closed]

At some point in 2015 I filled out a form and wrote 41 for my age. What are my possible birth years? Some trivial clarification about the information above: The age 41 is only exact up until the ...
-6
votes
1answer
788 views

What's My Number (Math Riddle) [closed]

I am thinking of a number. I multiplied by 3, subtracted by 8, doubled the result, and added 14. Then i added on 50% of what I had and subtracted 11. Then i divided by 5. After all that, I was left ...
9
votes
5answers
442 views

The oldest wins the prize, but they won't tell their age

I'm trying to design a problem that should be as close as possible to the following setup, while meeting some requirements about its solutions. Initial setup There is a group of more than 2 people ...
5
votes
2answers
424 views

Find age of John

Ten years before Alice's age is 4 times John's age. Ten years later, Alice's age is 2 times John's age. How old is John?
56
votes
12answers
17k 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 ...
1
vote
4answers
4k views

Fill 3x3 magic square with distinct numbers 1..60 summing up to 69

I have to fill a whole 3x3 grid in such a way that the sum of each row, column, and main diagonal is 69. I couldn't find any logic to fill it up. I have to use distinct numbers from 1 to 60 for this. ...
-2
votes
1answer
560 views

Measuring 4.6 liters with a 4.3L bucket and a 4.7L bucket

You are standing next to an unlimited source of water (the tap in your kitchen). You need precisely 4.6 litres of water. Luckily you found two empty buckets. One can hold 4.3 and the other 4.7 litres ...
11
votes
7answers
3k views

Longest arithmetic expression where the answer is equal to the number of letters

You can use any mathematical operations represented by English words. These English words must be found in a commonly used dictionary. Spaces are neither letters nor words. You can not use the same ...
6
votes
3answers
700 views

Ages of A and B (self-reference in past)

A says to B My age is twice of what your age was when I was of your age. B says to A If you add your current age to twice of your age when I was born, the answer is $63$. Assuming they both ...
47
votes
1answer
1k views

Self-referential Sudoku

I built this a while back but never had a good forum for it; this seems like the perfect spot to turn it loose. This is a 'traditional' Sudoku; cells are filled with numbers from 1 through 9, and all ...
36
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 ...
5
votes
4answers
650 views

A tour of 36 cities

Each of 4 people is touring 36 cities separately. Each of the 36 squares in the illustration below represents a city. To make the answers shorter, each city has been given a 1-character name, from A-Z,...
4
votes
1answer
259 views

What is the Sixth Number?

I'm thinking of 4 real numbers, $a,b,c$ and $d$ (they need not be integers, or even rational). There are 6 products you can make by multiplying pairs of these numbers, namely, $ab,ac,ad,bc,bd$ and $cd$...
34
votes
4answers
3k views

Display a number using a scientific calculator with most keys are stuck

Your have a scientific calculator such that most of the keys are unable to be pressed. The only keys that work are those for the functions $$ x^2 \;\; \sqrt{x} \;\; x!\;\; \exp\;\; \ln\;...
5
votes
1answer
786 views

Fit numbers on a grid with required sums for squares

Can anyone solve this puzzle or give me some tips? Rules: you have to use all 1, 2, 3, 4, 5, 6, 7 numbers in every 8 straight and vertical lines(4 vertical line and 4 straight line) And the summation ...
12
votes
1answer
844 views

Poring Over the Numbers: A Hidden Message

I thank my lucky stars I'm able to write this to you. I spent a hefty percentage of my remaining cash at the courier's office and I want to underscore the importance of this communique. If a man comes ...
2
votes
4answers
1k views

The Twins with a Different Age

Warning: To answer this riddle you need to have a thorough understanding of how time works. Two twins were born during the same year, on the same month, and the same day, exactly 10 minutes apart. ...
7
votes
2answers
3k views

Find the age of the ship and of the boiler

Some years back I was travelling by a cargo ship from New Zealand to Tahiti. I was curious to look around the ship one day and in the boiler room I asked a man how old the ship was. He smiled and ...
4
votes
3answers
606 views

A Second Benjamin Button

This was inspired by A curious case of Benjamin Button but has a different solution. In 1980 AD (or 1980 CE, if you prefer), Jack has an age of 20. In 1985 however, he is only 6 years old. How did ...
6
votes
1answer
509 views

A curious case of Benjamin Button

In 1980, Jack has an age of 20. In 1985 however, he is only 15 years old. How did he age backwards?
6
votes
2answers
534 views

Odd birthdate surprise

Last year, just before my birthday in February, I noticed something unsual. The last two digits of my birth year were the same as my age. How old was I then and was this an unusual occurrence?