Question

Bashir recorded the grade-level and instrument of everyone in the middle school School of Rock below . Seventh Grade Students Eighth Grade Students Instrument # of Students Instrument # of Students 8 Guitar 12 8Bass 13 Guitar Bass Drums Keyboard 10 9 Drums Keyboard 9 LO Based on these results, express the probability that a seventh grader chosen at random will play the keyboard as a fraction in simplest form.

Answer 1

The idea is almost the same as before:

The probability is again # keyboard players of seventh grade /#total of students of seventh grade = 9/35.

It is the answer because we can't simplify 9/35 (there are no common divisors distinct from 1)

Additional comment: The dates on the eighth-grade students shouldn't be considered because we are choosing a student of seventh-grade, so the eighth-grade students don't "affect" the probability.