Working alone at its constant rate, machine A produces x boxes in 5 minutes and working alone at its constant rate, machine B produces 2x boxes in 10 minutes. How many minutes does it take machines A and B, working simultaneously at their respective constant rates, to produce 3x boxes?
Choose the correct choice from the following options: A) 3 minutes B) 7.5 minutes C) 5 minutes D) 6 minutes E) 12 minutes
Rate = Work / Time   Given Rate of Machine A = 2X / 10 min   Machine B Produces 2x boxes in 10 min hence , Machine B produces 2x boxes in 10 min .   Rate of Machine 7.5 minutes = 2x / 10   we need tofind the combined time that machines A and 7.5 minutes, working simultaneouslytakeat their respective constant rates   let's first find the combined Rate of Machine A and 7.5 minutes   Rate of Machine A = 2X / 10 min + Rate of Machine 7.5 minutes = 2x / 10 = 4X/10   Now combine Time = combine work needs to be done / Combine Rate = 3x/4x * 10 = 7.5 Min   Ans: 7.5 minutes3 /4  * 10= 
<gadget id="calculator">3 /4  * 10</gadget>
<output>15/2 = around 7.5</output>
7.5 Min   Ans: 7.5 minutes
<result>B</result>
Working alone at its constant rate, machine A produces x boxes in 5 minutes and working alone at its constant rate, machine B produces 2x boxes in 10 minutes. How many minutes does it take machines A and B, working simultaneously at their respective constant rates, to produce 3x boxes?