Work Problems

1
Work Problems

• Section 7-8
• Page 326

2
The Work Formula

• Use this formula for all work problems. (It
  works!)
• Work Rate x Time Work Done
• rtw
• - Work Rate is the part of the job done in one
  unit of time. (If I paint a room in 4 hours, my
  work rate is ¼. This is the amount of the job I
  finish in one hour.)

3
Example of Work Rate

• Sheri can rake the lawn in 2 hours. Her work
  rate is the part of the job she can do in 1 hour.
  Therefore her work rate is ½ job per hour.
• If Tom can paint 2 rooms in 7 hours, what is his
  work rate? (how much of the job can he get done
  in 1 hour?)
• Answer 1/7

4
Example 2

• You can use a chart to organize work problems
  also. Remember you can set up the problem the
  same as a mixture problem.
• Josh can split a cord of wood in 4 days. His
  father can split a cord in 2 days. How long will
  it take them to split a cord of wood if they work
  together?

5
Example 2
-Let x be the number of days they complete it
together.
-Josh can do the job in 4 days, so his work rate
is ¼.
-Father can do the job in 2 days, so his work
rate is ½.
Work Rate Time Work Done
Josh ¼ x x/4
Father ½ x x/2
6
Example 2

• The work done by each man can be added together
  to get the entire job
• Joshs Part Fathers Part Whole Job
• x/4 x/2 1

7
Working out the Equation
8
Conclusion

• So it takes 4/3 of a day for the both of them to
  complete the work.
• Mixture problems and work problems can both be
  solved using organizational charts.

9
Homework

• Page 328-329 Problems 1-4