A theatre has 600 seats. Exactly 25% of these seats are filled. All of the people in the seats then move to an empty theatre that has 200 seats. What percentage of the seats in the smaller theatre are now filled?
Pick one
Solution
Since 25% of 600 is 10025×600=25×6=150, then 150 people move to the empty theatre.
The percentage of the seats now filled in the smaller theatre is $200150×100%=2150%=75%$.
Want a route through all this instead of an archive? The track
puts 2,444 problems in a working order, from Junior Challenge level to the IMO shortlist.