Choose any four digits (from 0, 1, 2, ... , 9) and place them in the cells below (you can repeat digits).
Read the two 2-digit numbers across and add them together.
Read the two 2-digit numbers down and add them too.
Then add these two totals together.
Try a few examples of your own.
Is there a quick way to tell if the total is going to be even or odd?
Can you make a total of 200?
How many ways are there of doing this?
If we use four 0s, the total would be 0.
If we use four 9s, the total would be 396.
Which numbers between 0 and 396 is it possible to make?
With thanks to Don Steward, whose ideas formed the basis of this problem.