A country has decided to have just two different coins, 3z and 5z coins. Which totals can be made? Is there a largest total that cannot be made? How do you know?

Charlie and Abi put a counter on 42. They wondered if they could visit all the other numbers on their 1-100 board, moving the counter using just these two operations: x2 and -5. What do you think?

Imagine you have a large supply of 3kg and 8kg weights. How many of each weight would you need for the average (mean) of the weights to be 6kg? What other averages could you have?

Can you find rectangles where the value of the area is the same as the value of the perimeter?

What size square corners should be cut from a square piece of paper to make a box with the largest possible volume?

Can you find the values at the vertices when you know the values on the edges?

Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?

Imagine a machine with four coloured lights which respond to different rules. Can you find the smallest possible number which will make all four colours light up?

This game challenges you to locate hidden triangles in The White Box by firing rays and observing where the rays exit the Box.

How does the time of dawn and dusk vary? What about the Moon, how does that change from night to night? Is the Sun always the same? Gather data to help you explore these questions.

Many natural systems appear to be in equilibrium until suddenly a critical point is reached, setting up a mudslide or an avalanche or an earthquake. In this project, students will use a simple. . . .

Can you guess the colours of the 10 marbles in the bag? Can you develop an effective strategy for reaching 1000 points in the least number of rounds?

Can you decode the mysterious markings on this ancient bone tool?

This problem offers you two ways to test reactions - use them to investigate your ideas about speeds of reaction.

Can you make a hypothesis to explain these ancient numbers?

This article explores the process of making and testing hypotheses.