Answer:
15 minutes
Step-by-step explanation:
The speed of the first machine is 1/10 job/minute.
The speed of the older machine is x.
Their combined speed is:
x + 1/10 = 1/6
Solving for x:
x = 1/6 − 1/10
x = 5/30 − 3/30
x = 2/30
x = 1/15
The speed of the older machine is 1/15 job/minute, so it takes 15 minutes for the older machine to do the job alone.
