Q. A and B can complete a piece of work in 12 days while B and C in 15 days. A did the work for 3 days, B for 8 days and C for 10 days to complete the work. In how many days C alone can complete the work?
Option
a)6 days
b)9 days
c)10 days
d)12days

• Ans d) 12 days
  
  Given A and B can complete a piece of work
  in 12 days while B and C in 15 days. A
  did the work for 3 days, B for 8 days
  and C for 10 days to complete the
  work.
  (A+B)'s 1 day work=1/12.(B+C)'s 1 day work=1/15
  Therefore 3(A+B)+5(B+C)+5C=1
  =)3(1/12)+5(1/15)+5C=1
  On solving we get C's 1 day work=1/12
  Therefore C alone can do the work in 12 days.
• 10 years agoHelpfull: Yes(24) No(5)
• (A+B+C)'s 1 day work be 1/x
  we know (A+B)'s 1 day work is 1/12 and
  (B+C)'s 1 day work is 1/15
  so, (A+B+C) - (A+B) = C = (1/x)-(1/12) = (12 - x)/12x
  (B+C) - C = B = (1/15) - ((12 - x)/12x) = (9x - 60)/60x
  (A+B) - B = A = (1/12) - ((9x - 60)/60x) = (60 - 4x)/60x
  now,
  A's 3 days work + B's 8 days work + C's 10 days work = 1
  (3*(60 - 4x)/60x) + (8*(9x - 60)/60x) + (10*(12 - x)/12x) = 1
  on solving above equation,we get
  x = 6
  then, C's 1 day work will be,
  C = (12 - 6)/(12*6)
  C = 1/12
  hence, C alone will complete the work in 12 days.
  so, ans = 12 days
• 10 years agoHelpfull: Yes(12) No(0)
• @varsha
  a-3 days,b-8 days=3+5,c-10days=3+5+2
  
  =>a+b+c worked for 3days,b+c for 5 days and c for 2 days
  =>3(a+b+c)+5(b+c)+2c=1
  =>3(a+b)+5(b+c)+5c=1
  =>3(1/12)+5(1/15)+5c=1
  =>c=1/12
  so 12 days
• 10 years agoHelpfull: Yes(3) No(0)
• ans is 12 days.
  (A+B)'s 3day work + (B+C)'s 5day work + C's 5 day work=1
  3/12 + 5/15 + c's 5day work =1 .hence c's 5 day work = 5/12 so i day work =1/12 ie C can do the work alone in 12 days.
• 10 years agoHelpfull: Yes(2) No(2)
• Can you explain how this equation was formed? 3(A+B)+5(B+C)+5C=1
• 10 years agoHelpfull: Yes(1) No(4)