Question 232142
melissa can clean the house in 4hours, whereas her husband, zack, can do the same job in 5 hours.
 They have agreed to clean together so that they can finish in the to watch a movie on TV that starts in 2 hours.
How long will it take them to clean the house together? Can they finish before the movie starts?
:
Let t = time required working together
:
Let the completed job (a clean house) = 1
:
{{{t/4}}} + {{{t/5}}} = 1
multiply by 20
5t + 4t = 20
9t = 20
t = {{{20/9}}}
t = 2.22 hrs, so no they can't, they will be about 13 min late