Sally is making spinners. As you can see from the diagram she has divided two circles into 4 equal parts. 
Now she is going to put numbers in the spaces on the circles.
Where should she put the numbers so that when she spins the two spinners and adds the numbers together each possible total comes up equally often? Do this for 1 possible total; 2 possible totals; 4 possible totals; 8 possible totals; and 16 possible totals. Why only those numbers of totals?