Xin 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 Guitar 15 Guitar 4 Bass 13 Bass13 Drums 12 Drums 13 Keyboard 3 Keyboard 5 Based on these results , express the probability that an eighth grader chosen at random will play the drums as a fraction in simplest form
The total number of eighth grade students is 35 (4 + 13 + 13 + 5 = 35).
The number of eighth grade students who play the drums is 13.
Therefore, the probability that an eighth grader chosen at random will play the drums is 13/35.