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"Work" Word Problems (page 3 of 4)
Convert their times to unit rates, making sure to convert "hours" to "minutes", so the units match:
minutes to complete
job: completed per minute: They weren't all working together for the first half hour; only Maria and Shaniqua were working. To figure how much they've completed, remember that (fraction of work) = (rate per unit) × (number of units): completed so far: Copyright © Elizabeth Stapel 19992011 All Rights Reserved ( ^{1}/_{100} + ^{1}/_{120} completed / minute) × (30 minutes) = ( ^{11}/_{600} completed / minute) × (30 minutes) = ( ^{11}/_{600} ) × (30) × (minutes / minute) × (completed) = 0.55 completed That means that 1 – 0.55 = 0.45 (or 45%) of the job remained when Liu joined them. Use the "(fraction of work) = (rate per unit) × (number of units)" construction to set up your equation, remembering to add Liu's labor for 20 minutes to the mix: finishing the job: ( ^{1}/_{100} + ^{1}/_{120} + ^{1}/t completed / minute) × (20 minutes) = 0.45 completed ( ^{11}/_{600} + ^{1}/t) × (20) = 0.45 ^{11}/_{600} + ^{1}/t = 0.0225 ^{1}/t = ^{1}/_{240} t = 240 That is, Liu's time for the task is 240 minutes, or four hours. << Previous Top  1  2  3  4  Return to Index Next >>



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