# SOLUTION: A large heating unit and small heating unit are being used to heat the water of a pool The large unit, working alone, requires 8 hours to heat the pool. After both units have bee

Algebra ->  Algebra  -> Rate-of-work-word-problems -> SOLUTION: A large heating unit and small heating unit are being used to heat the water of a pool The large unit, working alone, requires 8 hours to heat the pool. After both units have bee      Log On

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 Question 199351: A large heating unit and small heating unit are being used to heat the water of a pool The large unit, working alone, requires 8 hours to heat the pool. After both units have been working for 2 hours, the large unit is turned off. The small unit requires 7 more hours to complete the job of heating the water in the pool. How long would it take the small unit, working alone, to heat the pool water?Answer by ankor@dixie-net.com(15624)   (Show Source): You can put this solution on YOUR website!A large heating unit and small heating unit are being used to heat the water of a pool The large unit, working alone, requires 8 hours to heat the pool. After both units have been working for 2 hours, the large unit is turned off. The small unit requires 7 more hours to complete the job of heating the water in the pool. How long would it take the small unit, working alone, to heat the pool water? : Let x = time required by the small unit working alone Let the completed job (heating the pool) = 1 : Total time by the small unit: 2 + 7 = 9 hrs + = 1 Multiply equation by by 8x 8x* + 8x = 8x(1) Cancel out the denominators, results: 2x + 8(9) = 8x 72 = 8x - 2x 72 = 6x x = x = 12 hrs, small unit alone : : Check solution: 2/8 + 9/12 = 1