Machines A and B produce bottles at their respective constant rates. Machine A produces k bottles in 3 hours and machine B produces k bottles in 5 hours. How many hours does it take machines A and B, working simultaneously, to produce 16k bottles?
Pick one: A) 24 B) 26 C) 28 D) 30 E) 32
A's rate = k/3   B's rate = k/5   k/3 + k/5 = 8k/15   16k / (8k/15) = 30 hours   The answer is 30.16  / (8 /15)= 
<gadget id="calculator">16  / (8 /15)</gadget>
<output>30</output>
30 hours   The answer is 30.
<result>D</result>
Machines A and B produce bottles at their respective constant rates. Machine A produces k bottles in 3 hours and machine B produces k bottles in 5 hours. How many hours does it take machines A and B, working simultaneously, to produce 16k bottles?