There are **429** NRICH Mathematical resources connected to **Working systematically**, you may find related items under Using, Applying and Reasoning about Mathematics.

Can you find all the ways to get 15 at the top of this triangle of numbers? Many opportunities to work in different ways.

Use the numbers and symbols to make this number sentence correct. How many different ways can you find?

This challenge is about finding the difference between numbers which have the same tens digit.

In this calculation, the box represents a missing digit. What could the digit be? What would the solution be in each case?

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

Use two dice to generate two numbers with one decimal place. What happens when you round these numbers to the nearest whole number?

What happens when you round these numbers to the nearest whole number?

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

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

What two-digit numbers can you make with these two dice? What can't you make?

My local DIY shop calculates the price of its windows according to the area of glass and the length of frame used. Can you work out how they arrived at these prices?

In this game for two players, you throw two dice and find the product. How many shapes can you draw on the grid which have that area or perimeter?

Try this matching game which will help you recognise different ways of saying the same time interval.

What is the largest 'ribbon square' you can make? And the smallest? How many different squares can you make altogether?

How many possible necklaces can you find? And how do you know you've found them all?

How could you arrange at least two dice in a stack so that the total of the visible spots is 18?

Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!

What happens when you add three numbers together? Will your answer be odd or even? How do you know?

Advent Calendar 2011 - a mathematical activity for each day during the run-up to Christmas.

Can you see who the gold medal winner is? What about the silver medal winner and the bronze medal winner?

Can you use the information to find out which cards I have used?

In this problem it is not the squares that jump, you do the jumping! The idea is to go round the track in as few jumps as possible.

What could the half time scores have been in these Olympic hockey matches?

How could you put these three beads into bags? How many different ways can you do it? How could you record what you've done?

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

My dice has inky marks on each face. Can you find the route it has taken? What does each face look like?

Tom and Ben visited Numberland. Use the maps to work out the number of points each of their routes scores.

Two children made up a game as they walked along the garden paths. Can you find out their scores? Can you find some paths of your own?

What can you say about these shapes? This problem challenges you to create shapes with different areas and perimeters.

This cube has ink on each face which leaves marks on paper as it is rolled. Can you work out what is on each face and the route it has taken?

Sweets are given out to party-goers in a particular way. Investigate the total number of sweets received by people sitting in different positions.

My coat has three buttons. How many ways can you find to do up all the buttons?

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?

This task depends on groups working collaboratively, discussing and reasoning to agree a final product.

This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?

Can you put the numbers 1-5 in the V shape so that both 'arms' have the same total?

If you are given the mean, median and mode of five positive whole numbers, can you find the numbers?

Place the numbers 1 to 6 in the circles so that each number is the difference between the two numbers just below it.

A group of children are using measuring cylinders but they lose the labels. Can you help relabel them?

Different combinations of the weights available allow you to make different totals. Which totals can you make?

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

Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?

Add or subtract the two numbers on the spinners and try to complete a row of three. Are there some numbers that are good to aim for?

Use the differences to find the solution to this Sudoku.

These eleven shapes each stand for a different number. Can you use the number sentences to work out what they are?

If you hang two weights on one side of this balance, in how many different ways can you hang three weights on the other side for it to be balanced?

How many different triangles can you draw on the dotty grid which each have one dot in the middle?

Find the product of the numbers on the routes from A to B. Which route has the smallest product? Which the largest?

This Sudoku puzzle can be solved with the help of small clue-numbers on the border lines between pairs of neighbouring squares of the grid.