Algebraic Average
The mean of three numbers x, y and z is x. What is the mean of y and z?
Age
14 to 16
Challenge level
The mean of three numbers x, y and z is x.
What is the mean of y and z?
The sum of the three numbers x, y and z is 3x, so y + z = 2x.
So the mean of y and z is the same as the mean of 2x.
Therefore the mean of y and z is x.