The question is in the description.

Question

Given a grid with 15 sections, determine how many sections in the grid need to be shaded so the probability of a point chosen at random in the shaded area is exactly 0.8. Explain your reasoning.

Answer 1

Try it out.  Create a grid with 15 sections.  You know that theoretical probability says that the correct (shaded) outcomes is the numerator of a fraction, and the total number of outcomes is the denominator.  

 

The denominator is going to be 15, since you have 15 sections.  What would the numerator have to be so that the probability is 0.8?  You may want to convert the decimal into a fraction or percent.

 

 x  = 0.8

15