A metal company's old machine makes bolts at a constant rate of 100 bolts per hour. The company's new machine makes bolts at a constant rate of 150 bolts per hour. If both machines start at the same time and continue making bolts simultaneously, how many minutes will it take the two machines to make a total of 500 bolts?	Options:
A) 36
B) 72
C) 120
D) 144
E) 180
Old Machine   100 bolts in 60 mins   so,   5/3 bolts in 1 min   New Machine   150 bolts in 60 mins   so,   5/2 bolts in 1 min   together,   5/3 + 5/2 =   25/6 bolts in 1 min   so, for 500 bolts   500 * 6 / 25= 
<gadget id="calculator">500 * 6 / 25</gadget>
<output>120</output>
120 mins   Ans 120
<result>C</result>
A metal company's old machine makes bolts at a constant rate of 100 bolts per hour. The company's new machine makes bolts at a constant rate of 150 bolts per hour. If both machines start at the same time and continue making bolts simultaneously, how many minutes will it take the two machines to make a total of 500 bolts?