Ametal 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 300 bolts?

72 minutes

Explanation:

The combined rate of the two machines is 250 bolts/hr:

(100 bolts/hr) + (150 bolts/hr) = 250 bolts/hr

The number of bolts is equal to the rate multiplied by time, therefore an expression for time can be found:

Bolts = (rate)(time) >> Time = (bolts)/(rate)

The time necessary to make 300 bolts is:

Time = (bolts)/(rate)

Times = (300 bolts) / (250 bolts/hr) = 1.2 hr

The time in hours is converted to time in minutes as follows:

(1.2 hr) (60 min/hr) = 72 minutes

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