### Aufgabe 1

The numerator and denominator of Juan's fraction are positive integers whose sum is

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### Aufgabe 2

Rectangle intersects a circle at points

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### Aufgabe 3

Find the sum of digits of the number

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### Aufgabe 4

T-shirts were made in three colors, red, gray and blue. The number of red T-shirts is six smaller than the total number blue and gray T-shirts. Also, the number of gray T-shirts is ten smaller than the total number red and blue T-shirts. How many blue T-shirts were made?

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### Aufgabe 5

There are walnuts on the table in at least two piles. Each pile consists of at least walnuts. After moving one walnut from each pile to the first one, all piles will have the same number of walnuts. What was the original number of piles? Find all possibilities.

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### Aufgabe 6

A rectangle is divided by two segments parallel to its sides into four smaller rectangles. Let's label them

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### Aufgabe 7

Find pairwise distinct digits

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### Aufgabe 8

Find the area of a rectangle with perimeter cm and diagonal cm.

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### Aufgabe 9

Andrei took equally sized white cubes and used them to form one big cube

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### Aufgabe 10

What is the least possible number of members of a math circle, where girls form more than but less than of the members?

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### Aufgabe 11

If you increase the number of this problem by

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### Aufgabe 12

Find positive integer such that

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### Aufgabe 13

Find the smallest positive integer, which ends with number

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### Aufgabe 14

Each pair of consecutive digits of a

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### Aufgabe 15

A positive integer is called *awesome* if any other positive integer with the same sum of digits is greater. How many three-digit awesome numbers exist?

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### Aufgabe 16

Tim has found real numbers

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### Aufgabe 17

The numbers are arranged in some order to form a nine-digit integer. Consider all triplets of consecutive digits and add the corresponding seven three-digit numbers. What is the largest result that can be obtained?

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### Aufgabe 18

A real number is written in each cell of a square. Emily wrote down all products of two numbers from two distinct cells of the table and noticed that exactly of these products were negative. How many times did number appear in the original square? Find all possibilities.

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### Aufgabe 19

Math kingdom started to produce a new set of coins. On the first day they created coins with value MD (Math Dollar). Every other day they created coins with the smallest value which cannot be paid by at most ten existing coins. Which coins did they create on the

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### Aufgabe 20

Let the number be the solution to this problem. Find the probability that a randomly chosen point inside a unit square is at least units away from all sides.

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### Aufgabe 21

A square is filled with integers such that the sums of the horizontal rows increase by two going downwards and the sums of the vertical columns double from left to right. Given that the sum of the numbers in one of the rows is

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### Aufgabe 22

There are 2 boats, one on each side of a river bank. They both sail towards each other at a constant speed (not necessarily the same). The first time they meet, they are meters from one side of the bank. Once they reach the side of the bank, they turn around and move towards each other again. This time they meet meters from the other side of the bank. How wide is the river?

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### Aufgabe 23

Vertices of a star form a regular heptagon. What is the magnitude of the marked angle?

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### Aufgabe 24

Find such that

Note: the order of operations is:

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### Aufgabe 25

How many triplets of positive integers exist, such that

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### Aufgabe 26

A circle with radius

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### Aufgabe 27

Two nations and are in a battle with soldiers involved altogether. The armies take turns to attack. In each turn every living soldier from the attacking army shoots a soldier from the enemy's army. The battle ended (not necessarily by elimination of one of the sides) after three turns ( was shooting first, then and finally again). What is the least guaranteed number of survivors?

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### Aufgabe 28

All six sides of a convex hexagon are colored in red. Each of the diagonals is either blue or red. Find the number of such colorings that each triangle () has at least one red side.

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### Aufgabe 29

Malcom told each Michal and Shri a positive integer. Further, he told them, that the numbers they heard were distinct and that their sum is a two-digit number. Then the following conversation took place:

Michal: ”I cannot determine which one of us has the greater number.”

Shri: ”I can't determine it either, but I will tell you that my number is divisible by

Find the value of this sum, given that the logic Michal and Shri used was flawless.

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### Aufgabe 30

There are guests in a café, Turks and Indians. Each of them drinks either tea or coffee. An Indian speaks truth if he drinks tea and lies if he drinks coffee, whereas with the Turks it is the other way round. For questions ”Do you drink coffee?”, ”Are you Turkish?” and ”Is it raining outside?” the numbers of positive answers were

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### Aufgabe 31

Three digits were written to the end of a positive integer

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### Aufgabe 32

Alice, Betty, Claudia, Daniel, and Eli were playing doubles tournament in table-tennis. Each pair played against each other pair exactly once. Alice won games and Betty won games. How many games could Claudia win? Find all possibilities.

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### Aufgabe 33

Two players are playing a game on the given plan consisting of 30 cells. The rules are the following.

- players take turns,
- in one move a player colors one cell,
- in the first move, only a cell neighbouring with the edge can be colored. In any other moves, only a cell which is next to the last colored cell and is not further away from the center, can be colored,
- once a cell is colored, it cannot be colored again.
- the player who can no longer make a move, loses.

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### Aufgabe 34

In triangle with

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### Aufgabe 35

Ten people in the theater are sitting next to each other in one row. After a break they sit in a new arrangement, so that only two people remained in their original positions and the remaining eight sat next to their former position. In how many ways could they have done that?

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### Aufgabe 36

A positive integer is written on each face of a cube. To each vertex we assign the product of the numbers written on the three faces intersecting at that vertex. The sum of the numbers assigned to the vertices is

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### Aufgabe 37

Two bicyclists are racing on a straight path at constant speeds. They both start at one end and everytime they hit the end of the path, they turn around and go the opposite direction. Eventually, they meet again at one of the endpoints. Before that, the slower bicyclist had traveled the path times (in one of the directions) and the faster one times. How many times did they meet head on?

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### Aufgabe 38

Find the largest positive integer such that all its digits (other than the first one and the last one) are smaller than the arithmetic mean of the two surrounding digits.

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### Aufgabe 39

Two tetrominoes made of squares touch at points

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### Aufgabe 40

There are points with integral coordinates given in the plane. We connect each pair with a segment. How many of these segments are guaranteed to have a midpoint with integral coordinates?

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### Aufgabe 41

A five-digit integer is called *irreducible* if it cannot be written as a product of two three-digit integers. What is the maximum possible number of consecutive irreducible integers?

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### Aufgabe 42

Real numbers and satisfy

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### Aufgabe 43

A sequence is definned as follows:

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### Aufgabe 44

Let be an acute-angled triangle with altitudes

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### Aufgabe 45

Every guest at a party (including Tim) knows exactly seven boys and ten girls there. What is the least possible number of people at the party?

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### Aufgabe 46

Let be the midpoint of side of rectangle

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### Aufgabe 47

We write out all divisors of a positive integer which are less than from the greatest to the lowest. If is the sum of the second and third divisor, we say that is *additive*. How many additive numbers are there which are less than

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### Aufgabe 48

Find all real numbers such that

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### Aufgabe 49

A position of a minute hand and an hour hand on the clock is called *valid*, if it might occur during one hour cycle. Find the number of valid positions which remain valid after switching the two hands.

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### Aufgabe 50

Let

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### Aufgabe 51

Find all integers such that both and are perfect squares.

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### Aufgabe 52

A regular octahedron with side length is given in space. One circle is inscribed in one of the faces and another circle is circumscribed about an adjacent face. What is the minimal distance between the two circles?

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### Aufgabe 53

Let be a triangle with circumradius and inradius

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### Aufgabe 54

Real numbers

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