Given the rates of 5 semi-skilled and 4 skilled workers, can you find how long it takes 1 semi-skilled and 2 skilled workers to do a job?

• Working together, 4 skilled workers can complete a job in 5 days. However, 5 semi-skilled workers can complete the same job in 6 days. If 1 semi-skilled and 2 skilled workers work together, how long does it take for them to complete the same job?
• 9 years agoHelpfull: Yes(3) No(0)
• 7.5
  Working together, 4 skilled workers can complete a job in 5 days.
  therefore: 4 * 5 = 20 man-days for skilled men complete the job
  :
  However, 5 semi-skilled workers can complete the same job in 6 days.
  therefore: 5 * 6 = 30 man-days for semi-skilled men to complete the job
  :
  If 1 semi-skilled and 2 skilled workers work together, how long does it take for them to complete the same job?
  Let d = number of days for them to complete the job.
  Let the completed job = 1,
  
  Each group will do a fraction of the job, the two fractions add up to 1
  :
  %282d%29%2F20 + %281d%29%2F30 = 1
  multiply by 60, resulting in:
  3(2d) + 2(1d) = 60
  6d + 2d = 60
  8d = 60
  d = 60/8
  d = 7.5 days for them to complete the job together
• 10 years agoHelpfull: Yes(2) No(3)