Question

A machine makes 15 articles in half a hour
. How many articles will it make in (a) 1 hour, (b) 2
hours, (c) 5 hours?

Answer 1

Answer:

Say the rate of machine A is widgets per hour and the rate of machine B is widgets per hour. Since working together they can produce 1 widget in 3 hours, then their combined rate is widgets per hour. So, we have that:

.

Similarly the second equation would be:

.

Subtract the first equation from the second: widgets per hour. So, machine A needs 6 hours to produce 1 widget.