Question

Lydia 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 12 8 Bass 7. 13 Guitar Bass Drums Keyboard Drums Keyboard Based on these results, express the probability that a student chosen at random will play an instrument other than drums as a fraction in simplest form.

Answer 1

- 7th grade probability

P = (12 + 7 + 3) / (12 + 7 + 11 + 3)

P = 22/ 33

P = 2/3

- 8th grade probability

P = (8 + 13 + 7) / (8 + 13 + 4 + 7)

P = 28 / 32

P = 14/16 = 7/8

Both 7th and 8th grade

P = 2/3 * 7/8

P = 14/24

P = 7/12