Always try to be systematic in setting these scenarios up for analysis: If not already told, first describe an experiment, then the event, and then use the relevant formula:

• First, the experiment: select a fast food outlet specializing in Mexican food.
• Next, the event: E = the event that the outlet is none of the three named above.
• N = Sample size = 10,000 (given)
• Frequency of E, fr(E) = number of times E occurs = number of outlets other than the three named above = 10,000(4,809 + 430 + 275) = 4,486.

Now use the formula:

Experimental probability of E

=

fr(E) N

=

4,486 10,000

= 0.4486.