At the recent interdepartmental jam making contest, four lucky candidates took part to make the juiciest strawberry jam.
As it happens, the person who came last was the oldest. Glen was three years older than the person who came second. Drew was neither the oldest nor the youngest. Emery finished ahead of the 27-year-old, but didn't win. Alex was also unlucky this time, and didn't win either.
The ages of the contestants were 24, 27, 30 and 32.
Can you work out who finished where, and how old they were?
Reasoning
In 36 hours, Alex could empty 2 lots of bookshelves, Billie could also empty 2 lots of bookshelves, and Drew could refill 1 lot of bookshelves.
So, 2 + 2 – 1 = 3 lots of bookshelves in 36 hours. Which is 12 hours for one lot of bookshelves.
Alternative Reasoning
Alex and Billie can each empty 1/18 of the bookshelves in 1 hour, but Drew will refill 1/36 of the bookshelves in one hour.
So in one hour we have 1/18 + 1/18 – 1/36 = 1/12.
So it would take 12 hours to empty the bookshelves.