Question

How many leaves on a tree diagram are needed to represent all possible combinations tossing a coin and rolling a dice

Answer 1

You could get 2 different outcomes if you tossed a coin (head or tail) and 6 different outcomes if you rolled a dice (1-6). There would be 2 branches for tossing a coin and then 6 leaves on each for all the outcomes of rolling a dice so 6*2=12. There would be 12 leaves.

Answer 2

The total number of outcomes of rolling a die      = 6
The total number of outcomes of  tossing a coin = 2

The total number of possible outcomes of executing both experiments is 6*2=12, which is also the number of leaves (end of the branch of a tree) on a tree diagram.