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Work problems

Work problems. #22: An experienced bricklayer constructs a small wall in 3 hours. The apprentice (you) completes the job in 6 hours. Find how long it takes if they work together . The answer is not 4.5 hours (no averaging!) The answer is not 9 hours (Makes no sense!!).

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Work problems

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  1. Work problems • #22: An experienced bricklayer constructs a small wall in 3 hours. The apprentice (you) completes the job in 6 hours. Find how long it takes if they work together. The answer is not 4.5 hours (no averaging!) The answer is not 9 hours (Makes no sense!!)

  2. An experienced bricklayer constructs a small wall in 3 hours. The apprentice (you) completes the job in 6 hours. Find how long it takes if they work together. Make a chart! Equation set-up: 1/3 + 1/6 = 1/x Solution: x = 2 hrs

  3. #21 Section 5.6 • Smith Engineering found that an experienced surveyor surveys a roadbed in 4 hours. An apprentice surveyor needs 5 hours to do the job. If the two work together, find how long it takes them to complete the job? • Set-up: LCD = 20x • 1/4+ 1/5 = 1/x Solution x = 20/9 hours

  4. #26: Distance = Rate X Time • A boat can travel 9 miles upstream in the same amount of time it takes to travel 11 miles downstream. If the current of the river is 3 mi/hr, complete the chart below and use it to find the speed of the boat in still water.

  5. A boat can travel 9 miles upstream in the same amount of time it takes to travel 11 miles downstream. If the current of the river is 3 mi/hr, complete the chart below and use it to find the speed of the boat in still water (let boat speed = x).Dist = rate x time  time = Dist/rate Set-up: 9(x+3) = 11 (x-3) 9x+27 = 11x-33 27+33 = 11x – 9x 60 = 2x 30 = x The speed of the boat in still water is 30 mi/hr

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