Question

Working alone at its constant rate, machine a takes 3 hours to produce a batch of identical computer parts. working alone at its constant rate, machine b takes 2 hours to produce an identical batch of parts. how long will it take the two machines, working simultaneously at their respective constant rates, to produce an identical batch of parts?

Answer 1

In 1 hour, A can produce = 1/3 batch
B can produce = 1/2 batch

In 1 hour, both can produce= 1/2 + 1/3 = 5/6 batch

To produce 1 batch, they need = 1/(5/6) = 6/5 hours = 1 hour 12 minute