This big box adds something to any number that goes into it. If you know the numbers that come out, what addition might be going on in the box?

Explore the relationship between quadratic functions and their graphs.

Explore the relationship between simple linear functions and their graphs.

Have a go at creating these images based on circles. What do you notice about the areas of the different sections?

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

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

Use the computer to model an epidemic. Try out public health policies to control the spread of the epidemic, to minimise the number of sick days and deaths.

Pick a square within a multiplication square and add the numbers on each diagonal. What do you notice?

Find the maximum value of n to the power 1/n and prove that it is a maximum.

Evaluate these powers of 67. What do you notice? Can you convince someone what the answer would be to (a million sixes followed by a 7) squared?

Many numbers can be expressed as the difference of two perfect squares. What do you notice about the numbers you CANNOT make?

In 15 years' time my age will be the square of my age 15 years ago. Can you work out my age, and when I had other special birthdays?

Two semicircle sit on the diameter of a semicircle centre O of twice their radius. Lines through O divide the perimeter into two parts. What can you say about the lengths of these two parts?

This challenge encourages you to explore dividing a three-digit number by a single-digit number.

Look at three 'next door neighbours' amongst the counting numbers. Add them together. What do you notice?

This ladybird is taking a walk round a triangle. Can you see how much he has turned when he gets back to where he started?

This article introduces the idea of generic proof for younger children and illustrates how one example can offer a proof of a general result through unpacking its underlying structure.

Look at what happens when you take a number, square it and subtract your answer. What kind of number do you get? Can you prove it?

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

A introduction to how patterns can be deceiving, and what is and is not a proof.

Can you find some Pythagorean Triples where the two smaller numbers differ by 1?

Can you find the values at the vertices when you know the values on the edges of these multiplication arithmagons?

Think of a two digit number, reverse the digits, and add the numbers together. Something special happens...

How many different colours of paint would be needed to paint these pictures by numbers?

Here is a machine with four coloured lights. Can you make two lights switch on at once? Three lights? All four lights?

Becky created a number plumber which multiplies by 5 and subtracts 4. What do you notice about the numbers that it produces? Can you explain your findings?

Steve has created two mappings. Can you figure out what they do? What questions do they prompt you to ask?

Alison has created two mappings. Can you figure out what they do? What questions do they prompt you to ask?

Explore Alex's number plumber. What questions would you like to ask? Don't forget to keep visiting NRICH projects site for the latest developments and questions.

Charlie has created a mapping. Can you figure out what it does? What questions does it prompt you to ask?

Drawing a triangle is not always as easy as you might think!

Investigate the sum of the numbers on the top and bottom faces of a line of three dice. What do you notice?

This problem is a sequence of linked mini-challenges leading up to the proof of a difficult final challenge, encouraging you to think mathematically. Starting with one of the mini-challenges, how. . . .

This group tasks allows you to search for arithmetic progressions in the prime numbers. How many of the challenges will you discover for yourself?

An investigation that gives you the opportunity to make and justify predictions.

A point moves on a line segment. A function depends on the position of the point. Where do you expect the point to be for a minimum of this function to occur.

Problem solving is at the heart of the NRICH site. All the problems give learners opportunities to learn, develop or use mathematical concepts and skills. Read here for more information.

If you'd like to know more about Primary Maths Masterclasses, this is the package to read! Find out about current groups in your region or how to set up your own.

Make a conjecture about the curved track taken by the complex roots of a quadratic equation and use complex conjugates to prove your conjecture.

Investigate and explain the patterns that you see from recording just the units digits of numbers in the times tables.

Join in this ongoing research. Build squares on the sides of a triangle, join the outer vertices forming hexagons, build further rings of squares and quadrilaterals, investigate.

Change the squares in this diagram and spot the property that stays the same for the triangles. Explain...

Proof does have a place in Primary mathematics classrooms, we just need to be clear about what we mean by proof at this level.

Make and prove a conjecture about the value of the product of the Fibonacci numbers $F_{n+1}F_{n-1}$.

What have Fibonacci numbers got to do with Pythagorean triples?

What have Fibonacci numbers to do with solutions of the quadratic equation x^2 - x - 1 = 0 ?

Show that all pentagonal numbers are one third of a triangular number.

Can you find a rule which relates triangular numbers to square numbers?