A can do 1/3 of the work in 5 days and B can do 2/5 of the work in 10 days. In how many days both A and B together can do the work?

(a) 7 1/4
(b) 8 4/5
(c) 9 3/8
(d) 10

• No of jobs
  or
  fraction Time in Rate in
  of job days job/day
  A working alone 1/3 5 (1/3)÷5 =(1/3)·(1/5)=1/15
  B working alone 2/5 10 (2/5)÷10 = (2/5)/50=1/25
  A&B working together 1 x 1/x
  
  1/15+1/25=1/x
  solve ans=9 3/8
  
  
  
  
  
  
  
  
  
  
  Multiply through by LCD = 75 and solve. You'll get x = 9 3/8 days.
  
• 11 years agoHelpfull: Yes(1) No(0)