Every student of a certain school must play an instrument

Every student of a certain school must play an instrument. In last year, 1/2 of the students picked a woodwind instrument, 2/5 of the students picked a brass instrument, and all of the other students took percussion. In this year, 1/2 of the students who play woodwind and 1/4 of the students who play brass instruments left school, other students did not leave, and no fresh student come in. What fraction of all students play either a woodwind or brass instrument?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #19090