SOLUTION: Jeff can weed the garden in 4 hours by himself. His wife Brenda takes the same amount of time to weed the garden. After they have worked for 1 hour, their son, Rory helps them to f

Question 335517: Jeff can weed the garden in 4 hours by himself. His wife Brenda takes the same amount of time to weed the garden. After they have worked for 1 hour, their son, Rory helps them to finish the job in 1/2 hour. How long would it have taken Rory and Brenda to do this entire weeding job (start to finish) together?
Answer by nyc_function(2741) (Show Source): You can put this solution on YOUR website!
let work involved = 4 units,
then J & B each work @ 1 unit/hr
ie J+B = 2
in 1 hr they do 2 units of work
2 more units remain
J+B+R finish 2 units of work in 1/2 hr, @ 4units/hr
so R works @ 2units/hr
B+R will work @ 1+2 = 3 units/hr
so they will take 4/3
= 1 1/3 h
= 1 h 20 m

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