A work is done by three person A,B and C. A alone takes 10 hours to complete a single product but B and C working together takes 4 hours, for the completion of the same product. If all of them worked together and completed 14 products, then how many hours have they worked?

A.

20 hrs

B.

28 hrs

C.

40 hrs

D.

54 hrs

• 1
  A
  =10 and
  1
  B
  +
  1
  C
  =
  1
  4
  (Given)
  1
  A
  +
  1
  B
  +
  1
  C
  =
  1
  4
  +
  1
  10
  =
  7
  20
  
  In 20 hours, working together they will complete 7 products.
  Thus in 40 hours they will complete 14 products
• 9 years agoHelpfull: Yes(0) No(0)
• work of A in 1 hour=1/10
  (B+C) in 1 hr=1/4
  A+B+C=(1/4+1/10) in 1 hr
  total product=14
  so total time=14/(1/10+1/4)=40hrs
  
• 9 years agoHelpfull: Yes(0) No(0)
• A=10=1/10
  B+C=4=1/4
  work together in 1hr-14
  A+B+C (in 1 hour)=1/10+1/4
  A+B+C=7/20
  7/20-14
  14*20/7=40hrs
• 7 years agoHelpfull: Yes(0) No(0)