A person finishes a certain work for 2 hours, another person finishes the same work for 4 hours. How much time will it take for the two to finish the work? (please explain how you solved this)

Lunar Apr 22, 2016

#1**+5 **

Notice that the first person does 1/2 the job in one hour and the second does 1/4 of the job in one hour.....so......together.......they complete 1/2 + 1/4 = 2/4 + 1/4 = 3/4 of the job in one hour

Now.....all you have to do is to invert this fraction, and it will give you the time that it will take both of them working together to complete the job = 4/3 hrs. = 1 + 1/3 hrs = 1 hr, 20 min

This makes sense....if you can complete 1/2 of a job in one hour.....it will take you the reciprocal of this fraction, time wise, to compllete the whole job = 2/1 hrs = 2 hrs

CPhill Apr 22, 2016