Question 1154714
Howard and Edward, working together, can complete a job in 12 hours.  Edward requires 18 hours to do this job alone.  Howard and Edward start the job.  After they worked for 4 hours, Howard left the job.  How many hours will Edward require to finish the job working alone?
<pre><b><u>6 hours is WRONG!!</b></u>
If both can do the job in 12 hours, then in 4 hours, they will have done: {{{matrix(1,5, 4/12, or, 1/3, of, job)}}}
With {{{1/3}}} of work completed by both, in 4 hours, {{{matrix(1,7, 1 - 1/3, or, 2/3, of, work, remains, undone)}}}
With Edward taking 18 hours to do entire job alone, and doing {{{1/18}}} of job in 1 hour, time (T) taken by Edward to complete remaining {{{2/3}}} of job is: {{{matrix(3,3, (1/18)/(2/3), "=", 1/T,
(1/18) * (3/2), "=", 1/T,
1/12, "=", 1/T)}}}
T, or time taken by Edward to complete remaining {{{2/3}}} of job = {{{highlight_green(highlight(matrix(1,2,12, hours)))}}}