17. Only tenth-, eleventh-, and twelfth-grade students

attend Washington High School. The ratio of tenth

graders to the school's total student population is

86:255, and the ratio of eleventh graders to the

school's total student population is 18:51. If 1 student

is chosen at random from the entire school, which

grade is that student most likely to be in?

Answer: Eleventh Grade

Step-by-step

The ratio of tenth graders to the school's total population is 86:255 = 33.7%.

The ratio of eleventh graders to the school's total population is 18:51 = 35.3%.

Since the probability of a student being in either tenth, eleventh, or twelfth grade = 1 = 100% (that is, certainty), then the probability of a randomly drawn student being in twelfth grade is (100-33.7-35.3) % = 31.0%.

When randomly choosing one student from the whole school, it is most likely (35.3%) that the student is in the eleventh grade.