Answer:
10 minutes.
Step-by-step explanation:
In this case we have that one machine ends in a quantity "m" of coins in 15 minutes and the other machine the same amount "m" in 30 minutes, that is:
Machine 1: m / 15
Machine 2: m / 30
Therefore, to know the performance of the two together, we must add:
m / 15 + m / 30 = m / x
We cancel m, and we are left with:
1/15 + 1/30 = 1 / x
0.1 = 1 / x
x = 1 / 0.1
x = 10
Therefore, the two machines together would take 10 minutes.
