Q:

P and Q can do a piece of work in 15 days, Q and R in  $$ {22{1\over 2}}$$ days, P and R in 30 days. They all work at it for 9 days and then P leaves but Q and R go on together for 6 days more. If then Q leaves, how long will R take to complete the work?

• 1
  14 days
• 2
  18 days
• 3
  15 days
• 4
  16 days
• 5
  12 days