Question

if 1000 articles of a given type can be returned out by a first machine in 8 hours, by a second in 5 hours, and by the third in 4 hours, how long will it take to turn out the articles with an machine working?

Answer 1

find each machine rate:
rate1=1000/8
rate2=1000/
rate3=1000/4

So I assume you want a combined rate.

rate= number per time

So in forty hours, machine2=1000/8hr*40hrs=5000
machine2=1000/5hr*40hrs =8000
machine3=1000/4hr*40hrs=10000

combined rate=23000/40hrs=575per hour