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Resources tagged with Combinatorics similar to Janusz Asked:

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Broad Topics > Decision Mathematics and Combinatorics > Combinatorics

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Transitivity

Stage: 5

Suppose A always beats B and B always beats C, then would you expect A to beat C? Not always! What seems obvious is not always true. Results always need to be proved in mathematics.

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Knight Defeated

Stage: 4 Challenge Level: Challenge Level:1

The knight's move on a chess board is 2 steps in one direction and one step in the other direction. Prove that a knight cannot visit every square on the board once and only (a tour) on a 2 by n board. . . .

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Ordered Sums

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

Let a(n) be the number of ways of expressing the integer n as an ordered sum of 1's and 2's. Let b(n) be the number of ways of expressing n as an ordered sum of integers greater than 1. (i) Calculate. . . .

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Postage

Stage: 4 Challenge Level: Challenge Level:1

The country Sixtania prints postage stamps with only three values 6 lucres, 10 lucres and 15 lucres (where the currency is in lucres).Which values cannot be made up with combinations of these postage. . . .

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Magic W Wrap Up

Stage: 5 Challenge Level: Challenge Level:1

Prove that you cannot form a Magic W with a total of 12 or less or with a with a total of 18 or more.

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Russian Cubes

Stage: 4 Challenge Level: Challenge Level:1

I want some cubes painted with three blue faces and three red faces. How many different cubes can be painted like that?

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Doodles

Stage: 4 Challenge Level: Challenge Level:1

Draw a 'doodle' - a closed intersecting curve drawn without taking pencil from paper. What can you prove about the intersections?

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N000ughty Thoughts

Stage: 4 Challenge Level: Challenge Level:1

How many noughts are at the end of these giant numbers?

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Counting Binary Ops

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

How many ways can the terms in an ordered list be combined by repeating a single binary operation. Show that for 4 terms there are 5 cases and find the number of cases for 5 terms and 6 terms.

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Magic W

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

Find all the ways of placing the numbers 1 to 9 on a W shape, with 3 numbers on each leg, so that each set of 3 numbers has the same total.

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Symmetric Tangles

Stage: 4

The tangles created by the twists and turns of the Conway rope trick are surprisingly symmetrical. Here's why!

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Cube Net

Stage: 5 Challenge Level: Challenge Level:2 Challenge Level:2

How many tours visit each vertex of a cube once and only once? How many return to the starting point?

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Plum Tree

Stage: 4 and 5 Challenge Level: Challenge Level:1

Label this plum tree graph to make it totally magic!

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More Beads

Stage: 5 Challenge Level: Challenge Level:2 Challenge Level:2

With red and blue beads on a circular wire; 'put a red bead between any two of the same colour and a blue between different colours then remove the original beads'. Keep repeating this. What happens?

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W Mates

Stage: 5 Challenge Level: Challenge Level:1

Show there are exactly 12 magic labellings of the Magic W using the numbers 1 to 9. Prove that for every labelling with a magic total T there is a corresponding labelling with a magic total 30-T.

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Walkabout

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

A walk is made up of diagonal steps from left to right, starting at the origin and ending on the x-axis. How many paths are there for 4 steps, for 6 steps, for 8 steps?

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Olympic Magic

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

in how many ways can you place the numbers 1, 2, 3 … 9 in the nine regions of the Olympic Emblem (5 overlapping circles) so that the amount in each ring is the same?

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Jluuis or Even Asutguus?

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Sixth challenge cipher

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Snooker Frames

Stage: 5 Challenge Level: Challenge Level:1

It is believed that weaker snooker players have a better chance of winning matches over eleven frames (i.e. first to win 6 frames) than they do over fifteen frames. Is this true?

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Lost in Space

Stage: 4 Challenge Level: Challenge Level:1

How many ways are there to count 1 - 2 - 3 in the array of triangular numbers? What happens with larger arrays? Can you predict for any size array?

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Ip?

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Seventh challenge cipher

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Up a Semitone?

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Fifth challenge cipher

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Semicircle

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Fourth challenge cipher

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Stage 5 Cipher Challenge

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?

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A Fine Thing?

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Second challenge cipher

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Vital?

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Third challenge cipher

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Deep Roots

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Find integer solutions to: $\sqrt{a+b\sqrt{x}} + \sqrt{c+d.\sqrt{x}}=1$

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The Eternity Puzzle

Stage: 5

A big prize was offered for solving The Eternity Puzzle, a jigsaw with no picture and every piece is the same on both sides. The finished result forms a regular dodecagon (12 sided polygon).

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Factorial Fun

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

How many divisors does factorial n (n!) have?

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Magic Caterpillars

Stage: 4 and 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Label the joints and legs of these graph theory caterpillars so that the vertex sums are all equal.

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Penta Colour

Stage: 4 Challenge Level: Challenge Level:1

In how many different ways can I colour the five edges of a pentagon red, blue and green so that no two adjacent edges are the same colour?

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Snowman

Stage: 4 Challenge Level: Challenge Level:1

All the words in the Snowman language consist of exactly seven letters formed from the letters {s, no, wm, an). How many words are there in the Snowman language?

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One Basket or Group Photo

Stage: 2, 3, 4 and 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Libby Jared helped to set up NRICH and this is one of her favourite problems. It's a problem suitable for a wide age range and best tackled practically.

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Tangles

Stage: 3 and 4

A personal investigation of Conway's Rational Tangles. What were the interesting questions that needed to be asked, and where did they lead?

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Euler's Officers

Stage: 4 Challenge Level: Challenge Level:1

How many different ways can you arrange the officers in a square?

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Links and Knots

Stage: 4 and 5

Some puzzles requiring no knowledge of knot theory, just a careful inspection of the patterns. A glimpse of the classification of knots, prime knots, crossing numbers and knot arithmetic.

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Scratch Cards

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

To win on a scratch card you have to uncover three numbers that add up to more than fifteen. What is the probability of winning a prize?

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Modular Knights

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Try to move the knight to visit each square once and return to the starting point on this unusual chessboard.

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Snooker

Stage: 5 Challenge Level: Challenge Level:1

A player has probability 0.4 of winning a single game. What is his probability of winning a 'best of 15 games' tournament?

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Molecular Sequencer

Stage: 4 and 5 Challenge Level: Challenge Level:2 Challenge Level:2

Investigate the molecular masses in this sequence of molecules and deduce which molecule has been analysed in the mass spectrometer.

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An Introduction to Computer Programming and Mathematics

Stage: 5

This article explains the concepts involved in scientific mathematical computing. It will be very useful and interesting to anyone interested in computer programming or mathematics.