Question 119332
Washing and detailing the 3 cars can be considered 1 job, since that
is all the problem is interested in.
(1 job / 2 hrs) + (1 job / 1.5 hrs) = 1 job / k hrs
{{{1/2 + 1/1.5 = 1 / k}}}
multiply both sides by 3
{{{1.5 + 2 = 3/k}}}
{{{3.5 = 3/k}}}
{{{k = 3/3.5}}}
{{{k = .857}}}hrs
{{{.857*60 = 51.42}}}
Working together, they can do the job in 51 min 25 sec approximately