Explaining, convincing and proving

problem

Down and along

Age

11 to 14

Challenge level

Can you work out the values of J, M and C in this sum?
problem

Other side

Age

11 to 14

Challenge level

Weekly Problem 8 - 2016
Can you work out the size of the angles in a quadrilateral?
problem

Equilateral pair

Age

11 to 14

Challenge level

Weekly Problem 39 - 2016
In the diagram, VWX and XYZ are congruent equilateral triangles. What is the size of angle VWY?
problem

Peter's primes

Age

14 to 16

Challenge level

Peter wrote a list of all the numbers that can be formed by changing one digit of the number 200. How many of Peter's numbers are prime?
problem

What's on the back?

Age

11 to 14

Challenge level

Four cards have a number on one side and a phrase on the back. On each card, the number does not have the property described on the back. What do the four cards have on them?
problem

Shared vertex

Age

11 to 14

Challenge level

Weekly Problem 38 - 2017
In the diagram, what is the value of $x$?
problem

Network trees

Age

14 to 18

Challenge level

Explore some of the different types of network, and prove a result about network trees.
problem

Proof sorter - circumference angles

Age

11 to 16

Challenge level
problem

Anti-magic square

Age

11 to 14

Challenge level

You may have met Magic Squares, now meet an Anti-Magic Square. Its properties are slightly different - can you still solve it?
interactivity
Proof sorter - quadratic equation

Age

14 to 18

Challenge level

This is an interactivity in which you have to sort the steps in the completion of the square into the correct order to prove the formula for the solutions of quadratic equations.