What is the probability of getting heads when flipping a coin and getting a number greater than or equal to 4 when rolling a single die?

To find the probability of two events occurring, you must multiply their individual probabilities.  

Thus, 

the probability of getting heads when flipping a coin is :

favorable outcomes/total outcomes = 1/2

The probability of getting a number greater than or equal to 4 when rolling a single die is:

favorable outcomes/total outcomes = 3/6 =1/2

Now, we have to multiply the two probabilities.

1/2 * 1/2 =  1/4

1/4 or 25% is the probability of the above events occurring.