P can complete a work in 12 days working 8 hours a day. Q can complete the same work in 8 days working 10 hours a day. If both P and Q work together, working 8 hours a day, in how many days can they complete the work?

A. 60/11
B. 61/11
C. 71/11
D. 72/11

• A. 60/11
  
  Total job is 12*8 = 96 P hrs or 10*8= 80 Q hrs
  96 P = 80 Q
  P = (80/96 )*Q = Q*5/6
  (P+Q)'s one day job = 8*Q*(1+5/6) =8*Q*11/6 = Q*44/3
  
  so [Q*44/3] job is done in one day
  80Q job is done in 80*3/44 = 60/11 days
  
• 12 years agoHelpfull: Yes(10) No(2)
• p works =8*12=96 hrs
  q works =10*8=80 hrs
  both working 8 hrs a day=8*X
  1/96 +1/80 = 1/8X
  5+6/60=11/60
  
• 10 years agoHelpfull: Yes(7) No(0)
• IN 1 DAY, WORKING 8 HOURS P CAN DO=1/12 PART OF A WORK
  SIMILARLY IN 1 DAY WORKING 10 HOURS ,Q CAN DO=1/8 PART OF A WORK
  SO IN 1 DAY WORKING 1 HOUR A, Q CAN DO=1/8*1/10 PART OF WORK
  HENCE IN I DAY WORKING 8 HOURS A DAY,Q CAN DO=1/8*1/10*8=1/10 PART OF WORK
  IN 1 DAY TOGETHER P AND Q CAN DO=1/10+1/12=11/60 PART OF WORK.
  THEREFORE THEY NEED 60/11 DAYS TO COMPLETE THEIR JOB WORKING FOR 8 HOURS A DAY..
  SO ANSWER IS 60/11.
• 9 years agoHelpfull: Yes(0) No(0)