A alone can do a work in 12 days and B alone in 18 days. If C takes twice as long as A and B together, how long will B and C together take to complete the same work

• ans is 8 days
  a=12 or 1/12 b=18 or 1/18
  a+b=(a*b)/(a+b) [short cut]
  ie. (12*18)/12+18==>(12*18)/30==>36/5
  Take reciprocal 5/36[due to shortcut formula]
  C takes twice as long as a+b
  so (a+b)'s 1 day work 5/36
  i.e c,s 2 days work is 5/36 because C takes twice as long as A+B
  so c's 1 day work 5/72
  so (b+c) 5/72+1/18=1/8
  b+c together coplete tha task in 8 days
  
• 12 years agoHelpfull: Yes(10) No(1)
• Ans=3 days
  
  A=12 or 1/12 B=18 or 1/18
  A+B=(A*B)/(A+B) [short cut]
  ie. (12*18)/12+18==>(12*18)/30==>36/5
  Take reciprocal 5/36[due to shortcut formula]
  C takes twice as long as A+B
  so C=(5/36)*2=5/18
  then B+C=(5/18)+(1/18)[In this step U may be use Shortcut formula]
  ==>6/18=3 days...
• 12 years agoHelpfull: Yes(9) No(6)
• 8 days.
  since,A's 1 day work=1/12.
  B's 1 day work=1/18.
  so, (A+B)'s 1 day work=(1/12+1/18)=5/36.
  a/c to the problem,
  C's 1 day work=5/36*2=5/72.
  hence,
  (B+C)'s 1 day work=(1/18+5/72)=1/8
  so, B and C can complete the work together in 8 days.
• 12 years agoHelpfull: Yes(3) No(1)
• a's 1 day work=1/12 b's 1 day work=1/18
  ab's 1 day work=216/30
  c=2ab=2(216/30)=216/15=72/5
  then c's 1 day work is 5/72
  bc=(1/18)+(5/72)=9/72=1/8
  bc's work together to complete the work in 8 days
  
• 11 years agoHelpfull: Yes(2) No(0)