A company owns a machine that will produce 100 light switches in four hours. Due to increased demand, a second machine capable of producing 100 light switches in three hours has been added.
Approximately how many hours will it take to produce 100 light switches using both machines working together?
To find the combined rate at which both machines produce light switches, we add their rates. The first machine produces 100 light switches in 4 hours, so its rate is 100/4 = 25 switches per hour. The second machine produces 100 light switches in 3 hours, so its rate is 100/3 ≈ 33.33 switches per hour. Together, their combined rate is 25 + 33.33 ≈ 58.33 switches per hour. To find the time to produce 100 light switches together, we divide the total number of switches by their combined rate: 100 / 58.33 ≈ 1.7 hours.
[Machine 1 = (100 swtches/4 hrs)] + [Machine 2(100 swtches/3hrs) ] = 59 swtches/ hr for both machines. = 100 (target production) /59 (switches for both machines) = 1.69 or 1.7 hrs
In 3 hours total production is 100 + (100*3/4) = 175 3 hours : 175 units ? Hours : 100 units ? Hours = 3 x 100 / 175 = 1.7 hours Or In 4 hours total production is 100 + (100*4/3) = 233 4 hours : 233 units ? Hours : 100 units ? Hours = 4 x 100 / 233 = 1.7 hours
Which part of IIA-CIA does this question belong? It's just a GMAT question))
Second machine will produce 50 switches in 1.5 hours. At the same time, first machine can produce 37 switches (100/4*1.5). That is, in first 1.5 hours, total 87 switches can be produced by both the machines. Hence, for additional 13 switches a little more than 1.5 hours will be taken. Hence, 1.7 hours is the correct answer.
Not sure how to do calculation but seeing the answer 1.7 hours seems low. It would be helpful if all CIA answers are explained for why an answer is correct and why the other choices were incorrect
I agree - other test question banks provide the explanations