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Stella, Roberto and Candace are putting together small model kits. Stella can put a kit together in 45 minutes, while it takes Roberto 36 minutes. When all three of them work together, they can complete a kit in 12 minutes. Which equation can be used to calculate how long it will take Candace to put a kit together if she works alone?

Respuesta :

Answer:

It will take 30 minutes.

Step-by-step explanation:

We can calculate their 'speed' making kits. Since Stella can put a kit is 45 minutes, then in 1 minute she does 1/45 of the job. For Roberto is 1/36. For Candace is an unkown number C. But we know that the 3 of them combined can make a kit in 12 minutes, so their speed combined allows them to put 1/12 of a kit in 1 minute, in other words:

1/45+1/36+C = 1/12

Hence C = 1/12-1/36-1/45 = 1/30

This means that Candace in 1 minute does 1/30 of the job, so she will need 30 minutes to put a kit toguether.

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