Question 908281
"Find the time for two people working together to complete a task if it takes them 4.5 hours and 6 hours individually." 
:
Let t = time to complete the job working together
Let the completed job = 1
:
Each will do a fraction of the job, the two fractions add up to 1
:
{{{t/4.5}}} + {{{t/6}}} = 1
multiply by 36, get rid of the denominators
36*{{{t/4.5}}} + 36*{{{t/6}}} = 1*36
Cancel the denominators and you have
8t + 6t = 36
14t = 36
t= 36/14
t = 2.57 hrs working together; that's, 2 + .57(60) = 2 hr 34.2 min