P, Q and R can do a work in 20, 30 and 60 days respectively. How many days does it need to complete the work if P does the work and he is assisted by Q and R on every third day?

Options
1) 10 days
2) 14 days
3) 15 days
4) 9 days

• 3) 15 days
  
  In three days work completed=3*(1/20)+(1/30)+(1/60)=1/5
  So the work will be completed in 3/(1/5)=15 days
• 9 years agoHelpfull: Yes(3) No(0)
• in one day p can finish (1/20)th part of work . in one day q can finish (1/30)th part of work
  in one day r can finish (1/60)th part of work
  so in two days p can finish (1/10)th part of work
  and in 3rd day both q and r will involve so work done on third day is (1/20)+(1/30)+(1/60)=(1/10)th
  assume 1 cycle = 3 days. for 1 cycle work done is (1/10)+(1/10)=(1/5)th
  so for 5 cycles total work will be completed
  Total work completed in 5 cycles=5*3 days=15 days (ans-15 days) option no.3
• 9 years agoHelpfull: Yes(1) No(0)
• work done by P in 1 day= 100/20= 5%
  work done by Q in 1 day= 100/30= 3.333%
  work done by R in 1 day= 100/60= 1.666%
  
  Now P is assisted by Q & R on every 3rd day
  so work completed on every 3rd day= 3*5 + 3.33+1.66 =20%
  the
  Now 20% work is completed in 3 days
  then 100% work wil be completed in (100/20) * 3= 15 days
• 9 years agoHelpfull: Yes(1) No(0)