Phil likes to collect baseball cards.  He buys a pack of twenty each week for a year, but then loses half of them one day in a fire.  How many baseball cards does Phil have left?
Since there are 20 cards in a pack and 52 weeks in a year, Phil starts by collecting 20*52= <<20*52=1040>>1040 baseball cards
He then loses half of them for 1040/2= <<1040/2=520>>520 cards remaining.
#### 520