<em><u>Answer</u></em>
5 hours
<em><u>Explanation</u></em>
The two working together can finish a job in
Also, working alone, one machine would take one hour longer than the other to complete the same job.
Let the slower machine working alone take x hours. Then the faster machine takes x-1 hours to complete the same task working alone.
Their combined rate in terms of x is
This should be equal to 20/9 hours.
Multiply through by;
Factor to get:
It is not feasible for the slower machine to complete the work alone in 4/9 hours if the two will finish in 20/9 hours.
Therefore the slower finish in 5 hours.