# Tagged Questions

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### Using jugs filled with water problem

Given jugs $m$ and $n$ liters (WLOG $m<n$) is it always possible to get all $i$, $0 \leq i \leq n ?$ If so, prove it. If not, explain which $i$ you can get. Is there also a minimum number ...
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A few nights ago I couldn't sleep and so started doing this: I would take a number and add up all of its digits to get a new number and then add up all of those digits and so on until there was only ...
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### Dividing 100% by 3 without any left

In mathematics, as far as I know, you can't divide 100% by 3 without having 0,1...% left. Imagine an apple which was cloned two times, so the other 2 are completely equal in 'quantity'. The totality ...
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### Condition for L and R to make the below scenario true?

You are a given a number N. N <= 10 ^ 9 . You are given a range of numbers L and R . ...
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### Show that 4*AB=CAB is not possible

Show that 4*AB=CAB is not possible.Each letter denotes a single digit.It could be noted that since LHS is a multiple of 4,thus RHS would also be a multiple of 4.That's all i conclude yet...
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### A 5x5 board has 25 cells.The numbers $\{1,2,3,4,5\}$ are written on every row,every column and the two main diagonals.

A 5x5 board has $25$ cells. The numbers $\{1,2,3,4,5\}$ are written on every row,every column and the two main diagonals without any repetition. If the sum of the numbers of the diagonal below the ...
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### Number-Theoretic Coin Puzzle

There are three piles of coins. You are allowed to move coins from one pile to another, but only if the number of coins in the destination pile is doubled. For example, if the first pile has 6 coins ...
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### Find a number leaving a particular remainder with 3 different numbers

I have the following question: Let $N$ be the greatest number that will divide $1305, 4665$ and $6905$, leaving the same remainder in each case. What is the sum of digits of $N$. My approach ...
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### Find the digits $A,B,C$ such that $ABC+BAC+CAB=ABBC$

A,B,C are distinct digits of a three digit number such that ...
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### The number 3211000 is 7-special

Define a positive integer $k$ to be $n$-special if it satisfies the following properties: It has $n$ digits (0, 1, ..., 9) The 1st digit is equal to the number of 0's in the decimal representation ...
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### $20$ hats problem [duplicate]

I've seen this tricky problem, where $20$ prisoners are told that the next day they will be lined up, and a red or black hat will be place on each persons head. The prisoners will have to guess the ...
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### Pascal's other triangle

Just a brainteaser question: Can you identify the generator of the following pattern of numbers?      Remark on any interesting patterns you see in the triangle.
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### Counting squares of maximum size in a rectangle

Given a rectangle of sides $m$ and $n$. $( m,n \in [1,1000] )$ We can cut the rectangle into smaller identical pieces such that each piece is a square having maximum possible side length with ...
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### When is $\frac{2^n+1}{n^2}$ an integer? [duplicate]

Can anyone see how to solve this number puzzle? Find all integers $n>1$ such that $$\frac{2^n+1}{n^2}$$ is an integer.
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### Find $x,y$ such that $x=4y$ and $1$-$9$ occur in $x$ or $y$ exactly once.

$x$ is a $5$-digits number, while $y$ is $4$-digits number. $x=4y$, and they used up all numbers from 1 to 9. Find $x,y$. Can someone give me some ideas please? Thank you.
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### Specific ten digit number

I'm trying to solve this little problem. So far no luck. Could anyone help? Thanks in advance :) What is the ten digit number such that the i-th digit is the number of i's in the number ( 0<= i ...
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### A tedious puzzle (but not homework)

There are 1000 light bulbs and 1000 tutors. All light bulbs are off. Tutor 1 goes flipping light bulb 1,2,3,4... tutor 2 then flips 2,4,6,8...tutor 3 then 3,6,9...etc until all 1000 tutors have done ...