Working alone, it takes Maria nine hours to dig a 10 ft by 10 ft hole. Darryl can dig the same hole in ten hours. How long would it take them if they worked together?

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Answer 1 · 2018-07-04T09:05:59

#4.7368421052631575\ text{hrs}#

Maria alone takes #9#hrs to dig a hole hence one hour work of Maria

#=1/9#

Darryl alone takes #10#hrs to dig the same hole hence one hour work of Darryl

#=1/10#

Now, the fraction of work done in one hour by Maria & Darryl working together

#=1/9+1/10#

If takes total #h# hrs for Maria & Darryl working together to complete the same work then

#h(1/9+1/10)=1#

#h=1/(1/9+1/10)#

#=1/(19/90)#

#=90/19#

#=4.7368421052631575\ text{hrs}#