harishsridharan wrote:
Machine X, working alone at a constant rate, produces w widgets in 15 minutes. Machine Y, working alone at a constant rate, takes twice as much time to produce w widgets. How long, working simultaneously at their respective rates, would it take both machines working together to complete 4w widgets?
Concept:
If X can do a piece of job in \(A\) minutes while Y and can do the same job in \(B\) minutes, working together they can finish the job in \(\frac{AB}{(A + B)}\) minutes.So, both machines can make \(w\) widgets in \(\frac{(15)(30)}{(15 + 30)} = 10\) minutes
Therefore, \(4w\) widgets can be made in \((4)(10) = 40\) minutes