If Machine X can produce 1,000 bolts in 4 hours and Machine Y can produce 1,000 bolts in 5 hours, in how many hours can Machines X and Y, working together at these constant rates, produce 1,000 bolts?

Question: If Machine X can produce 1,000 bolts in 4 hours and Machine Y can produce 1,000 bolts in 5 hours, in how many hours can Machines X and Y, working together at these constant rates, produce 1,000 bolts?

Solution:
Machine X can produce 100 bolts in 4 hrs.
In an hour X can produce 1000/4 = 250 bolts

Machine Y can produce 1000 bolts in 5 hrs.
In an hour Y can produce 1000/5 = 200 bolts

Together they can produce 250 + 200 = 450 bolts in an hour.
They will produce 1000 bolts in 1000/450 hours.
= 20/9 hours.