SOLUTION: 1. It takes Mom, Dad and Isabel two hours to shovel their driveway after a snow storm. If Dad worked alone, it would take him 4 hours to shovel the entire driveway by himself. If I

Algebra ->  Rational-functions -> SOLUTION: 1. It takes Mom, Dad and Isabel two hours to shovel their driveway after a snow storm. If Dad worked alone, it would take him 4 hours to shovel the entire driveway by himself. If I      Log On


   



Question 1033196: 1. It takes Mom, Dad and Isabel two hours to shovel their driveway after a snow storm. If Dad worked alone, it would take him 4 hours to shovel the entire driveway by himself. If Isabel worked alone, it would take her twice as long as Dad. How long would it take Mom to shovel the driveway herself?
Answer by ikleyn(52800) About Me  (Show Source):
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1. It takes Mom, Dad and Isabel two hours to shovel their driveway after a snow storm.
If Dad worked alone, it would take him 4 hours to shovel the entire driveway by himself.
If Isabel worked alone, it would take her twice as long as Dad.
How long would it take Mom to shovel the driveway herself?
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Dad's rate of work is 1%2F4 of the driveway per hour.

Isabel's rate of work is 1%2F8 of the driveway per hour.

Isabel's + Dad's combined rate of work is 1%2F4+%2B+1%2F8 = 3%2F8 of the driveway per hour.

Mom'w + Dad's + Isabel's combined rate of work is 1%2F2 of the driveway per hour.

Hence, Mom's rate of work is is 1%2F2+-+3%2F8 = 1%2F8 of the driveway per hour.

Can you now answer the question to the problem?

On joint-work problems see the lessons
    - Using Fractions to solve word problems on joint work,
    - Solving more complicated word problems on joint work,
    - Selected joint-work word problems from the archive
in this site.