Working systematically

problem
The ELISA test

Age

14 to 18

Challenge level

In 1% of cases, an HIV test gives a positive result for someone who is HIV negative. How likely is it that someone who tests positive has HIV?
problem
Who's who?

Age

11 to 16

Challenge level

Can you solve the clues to find out who's who on the friendship graph?
problem
Dice stairs

Age

7 to 11

Challenge level

Can you make dice stairs using the rules stated? How do you know you have all the possible stairs?
problem
Centred squares

Age

7 to 11

Challenge level

This challenge, written for the Young Mathematicians' Award, invites you to explore 'centred squares'.
problem
An equilateral triangular problem

Age

11 to 14

Challenge level

Take an equilateral triangle and cut it into smaller pieces. What can you do with them?
problem
Open boxes

Age

7 to 11

Challenge level

Can you work out how many cubes were used to make this open box? What size of open box could you make if you had 112 cubes?
$Build it \Up more$

problem
Build it up more

Age

7 to 11

Challenge level

This task follows on from Build it Up and takes the ideas into three dimensions!
problem
Build it up

Age

7 to 11

Challenge level

Can you find all the ways to get 15 at the top of this triangle of numbers? Many opportunities to work in different ways.
list
Working systematically - short problems

Age

11 to 16

A collection of short Stage 3 and 4 problems on Working Systematically.