text: For every 1000 fans, there are 500 home supporters, 200 away supporters and 300 who support neither club.\n\n3% of the home supporters have a record.  That's 15 people.\n5% of the away supporters have a record.  That's 10 people.\n4% of the rest have a record.  That's 12 people.\n\nIn total, 37 people out of 1000 have a record.  That's 3.7%.\n\nIf you pick a person at random and they have a record, the probability that they are a home supporter is 15/37.  That's 41%.