Multiple choice

At a manufacturing plant, a team of 4 engineers and 9 robots can complete a project in half the time it takes for a team of 4 robots and 7 engineers to finish the same project. Additionally, it is known that 3 robots can complete the project in 15 days. How many engineers working at the same pace can finish the same project in 15 days?

  1. 15

  2. 21

  3. 24

  4. 30

  5. a
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let R be the rate of a robot and E be the rate of an engineer. 3R = 1/15 project/day, so R = 1/45. The work equation (4E + 9R) * T = (4R + 7E) * 2T implies 4E + 9R = 8R + 14E, so R = 10E. Since R = 1/45, E = 1/450. To finish in 15 days, we need 1/15 / (1/450) = 30 engineers.

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