SOLUTION: kris can do a piece of work in 6 hours while mat can complete the same piece of work in 4 hours.how long will it take them to do a piece of work if they work togrther at the same r

Algebra ->  Rate-of-work-word-problems -> SOLUTION: kris can do a piece of work in 6 hours while mat can complete the same piece of work in 4 hours.how long will it take them to do a piece of work if they work togrther at the same r      Log On


   

Question 716622: kris can do a piece of work in 6 hours while mat can complete the same piece of work in 4 hours.how long will it take them to do a piece of work if they work togrther at the same rates??????? pleaseeeeee i need the solution so that i can review it clearly when how find the answer thank u :)
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
kris can do a piece of work in 6 hours 
So Kris's work rate is 1 job per 6 hours or 1_job%2F%286_hr%29 = 1%2F6job%2Fhr

matt can complete the same piece of work in 4 hours
So Matt's work rate is 1 job per 4 hours or 1_job%2F%284_hr%29 = 1%2F4job%2Fhr

how long will it take them to do a piece of work if they work togrther at the same rates?
Let the answer be x hours.
So their combined work rate is 1 job per x hours or 1_job%2F%28x_hr%29 = 1%2Fxjob%2Fhr

The equation comes from:

            %28matrix%287%2C1%2C%0D%0A%22Kris%27s%22%2Cwork%2Crate%2Cin%2Cjobs%2Cper%2Chour%29%29%22%22%2B%22%22%28matrix%287%2C1%2C%0D%0A%22Matt%27s%22%2Cwork%2Crate%2Cin%2Cjobs%2Cper%2Chour%29%29%22%22=%22%22

                            1%2F6%22%22%2B%22%221%2F4%22%22=%22%221%2Fx

Multiply through by LCD = 12x and get 2.4 hours or 2 hours and 24 minutes.


Edwin