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Expert: Sherry Wallin - 1/17/2009


Question
Here is the problem: J working alone can repair 2 sections of trail in r hrs. K working alone can repair 1 section in p hrs. How long will it take J & K to repair a trail 6 sections long if they work together?
Here's how I solved:
R1T1 +R2T2 = repairs
T(2/r + 1/p) = 6
T = 6rp/2p+r
Is this correct?
Thanks very much for your assistance!

Answer
I did the problem slightly different, however I do arrive at the same answer. J's rate is 1/3 job per r hours or 1/3r. K's rate is 1/6 per p hours or 1/6p. So there work together is 1 job (which is 6 sections of the trailer) so (1/3r +1/6p)t = 1 which results in (2p+r)t = 6pr or
t = 6pr/(2p+r).

Your technique appears to be correct.

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Sherry Wallin

Expertise

I can answer most questions up through Calculus and some in Number Theory and Abstract Algebra.

Experience

I have had my Bachelor's Degree since 1987 and have been a teacher since 1988. I earned my Masters Degree in Mathematics May 2010. I have been teaching at the same community college since 2002.

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I have taught 12 years at the community college level, medical college, and technical college as well as a high school instructor and alternative education instructor and charter school instructor.

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Master's GPA 3.56 Bachelor's GPA 3.34 Post grad work not degree related GPA 4.0

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