Simultaneous equations

problem
Another quadruple clue Sudoku

Age

11 to 16

Challenge level

This is a variation of sudoku which contains a set of special clue-numbers. Each set of 4 small digits stands for the numbers in the four cells of the grid adjacent to this set.
problem
Addition equation Sudoku

Age

11 to 14

Challenge level

You need to find the values of the stars before you can apply normal Sudoku rules.
problem
LCM Sudoku II

Age

11 to 18

Challenge level

You are given the Lowest Common Multiples of sets of digits. Find the digits and then solve the Sudoku.
problem
Battery modelling

Age

16 to 18

Challenge level

Find out how to model a battery mathematically
problem
In sum-mary

Age

11 to 14

Challenge level

What does the sum of these three numbers tell us about their product?
problem
Real(ly) numbers

Age

16 to 18

Challenge level

If x, y and z are real numbers such that: x + y + z = 5 and xy + yz + zx = 3. What is the largest value that any of the numbers can have?
problem
Coffee

Age

14 to 16

Challenge level

To make 11 kilograms of this blend of coffee costs £15 per kilogram. The blend uses more Brazilian, Kenyan and Mocha coffee... How many kilograms of each type of coffee are used?
problem
Whole numbers only

Age

11 to 14

Challenge level

Can you work out how many of each kind of pencil this student bought?
problem
Surds

Age

14 to 16

Challenge level

Find the exact values of x, y and a satisfying the following system of equations: 1/(a+1) = a - 1 x + y = 2a x = ay
problem
All square

Age

11 to 14

Challenge level

Solve the system of equations xy = 1 yz = 4 zx = 9