In a random sample of 30 sixth graders, 9 has traveled outside of the united states. there are a total of 120 sixth graders in the school. predict how many students have traveled outside of the united states.

The first thing we must do is find the percentage that has traveled outside of the United States.
 For this, we make the following rule of three:
 30 > 100%
 9 > x
 We clear the value of x:
 x = (9/30) * (100)
 x = 30%
 Then, for 120 sixth graders in the school we have:
 (0.30) * (120) = 36
 
 36 students have traveled outside of the united states