Question #f5a07

1 Answer
Jan 5, 2017

Answer:

First, we must find out how much of the job remains and then how long the two will need.

Explanation:

The first sec. worked for 2 hours and so completed a fraction #2/8=1/4# of the job, leaving #3/4# of the job to do.
If they now both work for #x# hours, the first will complete #x/8# of the job and the second #x/10#.
So we need to solve #3/4=x/8+x/10#.

Multiplying both sides by 40 gives #30=5x+4x=9x#.
And so #x=10/3# hours or 3 hours and 20 minutes.