P and Q can complete a work in 20 days and 12 days respectively. P alone started the work and Q joined him after 4 days till the completion of the work. How long did the work last?

Options
1) 5 days
2) 10 days
3) 14 days
4) 22 days

• Answer is 10 days
  Lets total work is LCM of 20 and 12 = 60
  P's 1 day work = 60/20 = 3
  Q's 1 day work = 60/12 = 5
  since P did extra work for 4 days alone. So P's 4 days work = 3 x 4 = 12
  Work left for P and Q together = 60-12 = 48
  P and Q together 1 day work = 3+5 = 8
  time taken by Pand Q together = 48/8=6 days
  Hence work lasts for 6 + 4 = 10 days.
• 9 years agoHelpfull: Yes(0) No(0)
• P worked for 4 days = (4/20) => 1/5 (Completed work)
  Remaining work = 4/5
  P+Q Together working to complete remaining work = 1/20+1/12 => 32/240 => 2/15
  Remaining work will be completed in 4/5* 15/2 = 6 days
  P's work days +(P+Q work days ) = 4+6 = 10
• 2 years agoHelpfull: Yes(0) No(0)