Answer:
[tex]\frac{13}{18}[/tex] (72.22%)
Step-by-step explanation:
For this question, you must get at least one blue block. However, you can also think of it this way: pretend the other seven blocks are red (it does not matter since the colors other than blue do not matter) what is the probability that you do not only get red blocks?
You can calculate the probability that you only get red blocks simply with multiplication rule:
[tex]\frac{7}{9} *\frac{6}{8} *\frac{5}{7} *\frac{4}{6}[/tex][tex]=\frac{5}{18}[/tex]
(not the numbers increment down because they are not replaced)
Then, you use the fact that having red blocks and not having red blocks as a complement to calculate the probability
[tex]1-\frac{5}{18}[/tex][tex]=\frac{13}{18}[/tex]
This is your final answer: 72.22%
