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Broad Topics > Using, Applying and Reasoning about Mathematics > Working systematically

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A First Product Sudoku

Stage: 3 Challenge Level: Challenge Level:1

Given the products of adjacent cells, can you complete this Sudoku?

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Multiplication Squares

Stage: 2 Challenge Level: Challenge Level:1

Can you work out the arrangement of the digits in the square so that the given products are correct? The numbers 1 - 9 may be used once and once only.

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Neighbours

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

In a square in which the houses are evenly spaced, numbers 3 and 10 are opposite each other. What is the smallest and what is the largest possible number of houses in the square?

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Calendar Cubes

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Make a pair of cubes that can be moved to show all the days of the month from the 1st to the 31st.

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Elf Suits

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

If these elves wear a different outfit every day for as many days as possible, how many days can their fun last?

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Multiply the Addition Square

Stage: 3 Challenge Level: Challenge Level:1

If you take a three by three square on a 1-10 addition square and multiply the diagonally opposite numbers together, what is the difference between these products. Why?

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Button-up Some More

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

How many ways can you find to do up all four buttons on my coat? How about if I had five buttons? Six ...?

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I've Submitted a Solution - What Next?

Stage: 1, 2, 3, 4 and 5

In this article, the NRICH team describe the process of selecting solutions for publication on the site.

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Sweets in a Box

Stage: 2 Challenge Level: Challenge Level:1

How many different shaped boxes can you design for 36 sweets in one layer? Can you arrange the sweets so that no sweets of the same colour are next to each other in any direction?

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Mystery Matrix

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

Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.

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Multiples Sudoku

Stage: 3 Challenge Level: Challenge Level:1

Each clue in this Sudoku is the product of the two numbers in adjacent cells.

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Star Product Sudoku

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

The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the $9\times9$ grid.

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Home City

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

Use the clues to work out which cities Mohamed, Sheng, Tanya and Bharat live in.

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How Old Are the Children?

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

A student in a maths class was trying to get some information from her teacher. She was given some clues and then the teacher ended by saying, "Well, how old are they?"

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Ones Only

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.

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Latin Squares

Stage: 3, 4 and 5

A Latin square of order n is an array of n symbols in which each symbol occurs exactly once in each row and exactly once in each column.

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Broken Toaster

Stage: 2 Short Challenge Level: Challenge Level:1

Only one side of a two-slice toaster is working. What is the quickest way to toast both sides of three slices of bread?

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Factor Lines

Stage: 2 and 3 Challenge Level: Challenge Level:2 Challenge Level:2

Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.

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The Moons of Vuvv

Stage: 2 Challenge Level: Challenge Level:1

The planet of Vuvv has seven moons. Can you work out how long it is between each super-eclipse?

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Seven Pots of Plants

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

There are seven pots of plants in a greenhouse. They have lost their labels. Perhaps you can help re-label them.

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A Mixed-up Clock

Stage: 2 Challenge Level: Challenge Level:1

There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?

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Team Scream

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

Seven friends went to a fun fair with lots of scary rides. They decided to pair up for rides until each friend had ridden once with each of the others. What was the total number rides?

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Curious Number

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?

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Multiply Multiples 2

Stage: 2 Challenge Level: Challenge Level:1

Can you work out some different ways to balance this equation?

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It Figures

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

Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?

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Multiply Multiples 1

Stage: 2 Challenge Level: Challenge Level:1

Can you complete this calculation by filling in the missing numbers? In how many different ways can you do it?

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Multiply Multiples 3

Stage: 2 Challenge Level: Challenge Level:1

Have a go at balancing this equation. Can you find different ways of doing it?

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Shopping Basket

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

A mathematician goes into a supermarket and buys four items. Using a calculator she multiplies the cost instead of adding them. How can her answer be the same as the total at the till?

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Palindromic Date

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

What is the date in February 2002 where the 8 digits are palindromic if the date is written in the British way?

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5 on the Clock

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

On a digital clock showing 24 hour time, over a whole day, how many times does a 5 appear? Is it the same number for a 12 hour clock over a whole day?

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Eight Queens

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

Place eight queens on an chessboard (an 8 by 8 grid) so that none can capture any of the others.

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1 to 8

Stage: 2 Challenge Level: Challenge Level:1

Place the numbers 1 to 8 in the circles so that no consecutive numbers are joined by a line.

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Pouring the Punch Drink

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2 litres. Find a way to pour 9 litres of drink from one jug to another until you are left with exactly 3 litres in three of the jugs.

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All the Digits

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

This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?

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Multiples Grid

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

What do the numbers shaded in blue on this hundred square have in common? What do you notice about the pink numbers? How about the shaded numbers in the other squares?

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Ancient Runes

Stage: 2 Challenge Level: Challenge Level:1

The Vikings communicated in writing by making simple scratches on wood or stones called runes. Can you work out how their code works using the table of the alphabet?

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Family Tree

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Use the clues to find out who's who in the family, to fill in the family tree and to find out which of the family members are mathematicians and which are not.

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How Much Did it Cost?

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

Use your logical-thinking skills to deduce how much Dan's crisps and ice-cream cost altogether.

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Chocoholics

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

George and Jim want to buy a chocolate bar. George needs 2p more and Jim need 50p more to buy it. How much is the chocolate bar?

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Cuboids

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

Find a cuboid (with edges of integer values) that has a surface area of exactly 100 square units. Is there more than one? Can you find them all?

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Stairs

Stage: 1 and 2 Challenge Level: Challenge Level:1

This challenge is to design different step arrangements, which must go along a distance of 6 on the steps and must end up at 6 high.

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The Pied Piper of Hamelin

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

This problem is based on the story of the Pied Piper of Hamelin. Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!

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Adding Plus

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

Can you put plus signs in so this is true? 1 2 3 4 5 6 7 8 9 = 99 How many ways can you do it?

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Plate Spotting

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

I was in my car when I noticed a line of four cars on the lane next to me with number plates starting and ending with J, K, L and M. What order were they in?

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Octa Space

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

In the planet system of Octa the planets are arranged in the shape of an octahedron. How many different routes could be taken to get from Planet A to Planet Zargon?

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Symmetry Challenge

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Systematically explore the range of symmetric designs that can be created by shading parts of the motif below. Use normal square lattice paper to record your results.

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The Problem-solving Classroom

Stage: 1 and 2 Challenge Level: Challenge Level:1

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Calcunos

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

If we had 16 light bars which digital numbers could we make? How will you know you've found them all?

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Bean Bags for Bernard's Bag

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

How could you put eight beanbags in the hoops so that there are four in the blue hoop, five in the red and six in the yellow? Can you find all the ways of doing this?

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Diagonal Product Sudoku

Stage: 3 and 4 Challenge Level: Challenge Level:1

Given the products of diagonally opposite cells - can you complete this Sudoku?