Answer:
4% of all adults go to a health club at least twice a week
Step-by-step explanation:
the proportion of adults who belong to health clubs is 10% that is 0.10
the proportion of these adults (health club members) who go to the club at least twice a week is 40%, which is 0.40.
Thus, the proportion of all adults who go to a health club at least twice a week is
0.10 × 0.40 = 0.04, that is 4%
