Question 653004
Together Bill and Fred working at the same rate rake a yard in an hour and a half.
 If three of their friends had joined them at the start and also worked at
 the rate, it would have taken them ___ minutes for the five of them to
 rake the yard.
:
let the completed job = 1
Find the rate (r) using Bill and Fred 
:
{{{1.5/r}}} + {{{1.5/r}}} = 1
Multiply by r
1.5 + 1.5 = r
r = 3 hrs for one man to do the job
:
Let t = time required for 5 to do it
:
{{{t/3}}} + {{{t/3}}} + {{{t/3}}} + {{{t/3}}} + {{{t/3}}} = 1
{{{(5t)/3}}} = 1
5t = 3
t = 3/5 * 60 min = 36 min when all 5 do the job