Question 901827
x/10+x/6=1
x=15/4=x = 3.7500 for the two pumps to do the job together from the start
The large pump did half the job in the first 3 hours
3/6+x/10+x/6=1
x=15/8 = 1.8750 hours
So they need less than 2 hours to finish the job together

So it should take less than 3 hours for them both to finish the job.