Posted by MAnny on .
Daniel can plant an acre of corn in 6 hours. Working with Amanda, they can plant an acre of corn in 2 hours. How long would it take in hours for Amanda to plant an acre of corn by herself?

algebra 
bobpursley,
in six hours, they plant three acres (an acre each 2 hrs). But in those six hours, Dan planted one acre, so Amanda, the speedster, must have planted 5 acres.
Amanda rate 5 acres/6hrs or 5/6 acre/hr
so, her time for one acre is 6/5 hour. 
algebra  Hmmm 
Steve,
Where did the 5 come from? Amanda planted 2 acres, while Dan planted 1.
1/2 = 1/A + 1/6
A = 3 
algebra 
bobpursley,
You are right, I need to wear glasses at my computer.
In those six hours, Dan planted one acre, so Amanda planted two.