A chemistry teacher is able to grade chemistry labs at a rate of 5 labs for every 3 minutes. They need to grade 165 labs how many hours will it take?

1.65hr

Explanation:

Given parameters:

Number of labs  = 5 labs

 Time taken  = 3 minutes

Unknown:

Time taken in hours to grade 165 labs  = ?

Solution:

Let us find the rate of the teacher;

  Rate  =  

  Insert the parameters and solve;

   Rate  =   = 1.67labs/min

Now;

   Time to grade 165 labs  =  

   Time to grade 165 labs  =   = 98.8min

  Since;

               60min = 1hr

               98.8min  =   = 1.65hr

b is the correct answer

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