Assign the digits 0 through 9 to the letters below to create valid sums. Each letter stands for a unique digit, and all occurrences of that letter stand for the same digit. (For instance, if A = 6, ...

The sum shown below appears to be nothing out of the ordinary. The figures add up correctly as you would expect. But it has a rather unusual property. This is a cipher sum. Each of the digits ...

Deep in the jungle, the explorer Dr Quiverbone has chanced on a civilisation that has invented its own deletion arithmetic. In the example shown above, the first two rows added together give the third ...