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There are **31** NRICH Mathematical resources connected to **Algorithms**, you may find related items under Decision mathematics and combinatorics.

Problem
Primary curriculum
Secondary curriculum
### Probably a Code?

Is the regularity shown in this encoded message noise or structure?

Age 16 to 18

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Method in Multiplying Madness?

Watch our videos of multiplication methods that you may not have met before. Can you make sense of them?

Age 7 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Sorted

How can you quickly sort a suit of cards in order from Ace to King?

Age 14 to 18

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Stage 5 Cipher Challenge

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

Age 16 to 18

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### The Best Square

How would you judge a competition to draw a freehand square?

Age 16 to 18

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Happy birthDay

Can you interpret this algorithm to determine the day on which you were born?

Age 16 to 18

Challenge Level

Article
Primary curriculum
Secondary curriculum
### An Introduction to Computer Programming and Mathematics

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.

Age 16 to 18

Problem
Primary curriculum
Secondary curriculum
### Peaches in General

It's like 'Peaches Today, Peaches Tomorrow' but interestingly generalized.

Age 14 to 16

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Zeller's Birthday

What day of the week were you born on? Do you know? Here's a way to find out.

Age 14 to 16

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Unusual Long Division - Square Roots Before Calculators

However did we manage before calculators? Is there an efficient way to do a square root if you have to do the work yourself?

Age 14 to 16

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Procedure Solver

Can you think like a computer and work out what this flow diagram does?

Age 16 to 18

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Stretching Fractions

Imagine a strip with a mark somewhere along it. Fold it in the middle so that the bottom reaches back to the top. Stetch it out to match the original length. Now where's the mark?

Age 14 to 16

Challenge Level

Article
Primary curriculum
Secondary curriculum
### On What Day Did it Happen?

Read this article to find out the mathematical method for working out what day of the week each particular date fell on back as far as 1700.

Age 5 to 14

Article
Primary curriculum
Secondary curriculum
### Tournament Scheduling

Scheduling games is a little more challenging than one might desire. Here are some tournament formats that sport schedulers use.

Age 11 to 16

Article
Primary curriculum
Secondary curriculum
### Divided Differences

When in 1821 Charles Babbage invented the `Difference Engine' it was intended to take over the work of making mathematical tables by the techniques described in this article.

Age 16 to 18

Problem
Primary curriculum
Secondary curriculum
### X Marks the Spot

When the number x 1 x x x is multiplied by 417 this gives the answer 9 x x x 0 5 7. Find the missing digits, each of which is represented by an "x" .

Age 11 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Tis Unique

This addition sum uses all ten digits 0, 1, 2...9 exactly once. Find the sum and show that the one you give is the only possibility.

Age 11 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Slippy Numbers

The number 10112359550561797752808988764044943820224719 is called a 'slippy number' because, when the last digit 9 is moved to the front, the new number produced is the slippy number multiplied by 9.

Age 11 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Vedic Sutra - All from 9 and Last from 10

Vedic Sutra is one of many ancient Indian sutras which involves a cross subtraction method. Can you give a good explanation of WHY it works?

Age 14 to 16

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Medal Muddle

Countries from across the world competed in a sports tournament. Can you devise an efficient strategy to work out the order in which they finished?

Age 11 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Alphabet Soup

This challenge is to make up YOUR OWN alphanumeric. Each letter represents a digit and where the same letter appears more than once it must represent the same digit each time.

Age 11 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Skeleton

Amazing as it may seem the three fives remaining in the following `skeleton' are sufficient to reconstruct the entire long division sum.

Age 11 to 14

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Triangle Incircle Iteration

Keep constructing triangles in the incircle of the previous triangle. What happens?

Age 14 to 16

Challenge Level

Problem
Primary curriculum
Secondary curriculum
### Route to Root

A sequence of numbers x1, x2, x3, ... starts with x1 = 2, and, if you know any term xn, you can find the next term xn+1 using the formula: xn+1 = (xn + 3/xn)/2 . Calculate the first six terms of this sequence. What do you notice? Calculate a few more terms and find the squares of the terms. Can you prove that the special property you notice about this sequence will apply to all the later terms of the sequence? Write down a formula to give an approximation to the cube root of a number and test it for the cube root of 3 and the cube root of 8. How many terms of the sequence do you have to take before you get the cube root of 8 correct to as many decimal places as your calculator will give? What happens when you try this method for fourth roots or fifth roots etc.?

Age 16 to 18

Challenge Level