working alone at its constant rate, machine a produces x boxes in 10 minutes and working alone at its constant rate, machine b produces 2 x boxes in 5 minutes. how many minutes does it take machines a and b, working simultaneously at their respective constant rates, to produce 4 x boxes?	Choose the correct choice from the following options:
A) 3 minutes
B) 4 minutes
C) 5 minutes
D) 6 minutes
E) 8 minutes
<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">10 / 10</gadget>
<output>1</output>

<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">40 / 5</gadget>
<output>8</output>

<result>E</result>
working alone at its constant rate, machine a produces x boxes in 10 minutes and working alone at its constant rate, machine b produces 2 x boxes in 5 minutes. how many minutes does it take machines a and b, working simultaneously at their respective constant rates, to produce 4 x boxes?
divide(multiply(4, 10), add(speed(10, 10), speed(multiply(2, 10), 5)))
rate = work / time given rate of machine a = x / 10 min machine b produces 2 x boxes in 5 min hence , machine b produces 4 x boxes in 10 min . rate of machine b = 4 x / 10 we need tofind the combined time that machines a and b , working simultaneouslytakeat their respective constant rates let ' s first find the combined rate of machine a and b rate of machine a = x / 10 min + rate of machine b = 4 x / 10 = 5 x / 10 now combine time = combine work needs to be done / combine rate = 4 x / 5 x * 10 = 8 min ans : e