SOLUTION: I have been unable to come up with an equation to solve this problem. Could I get some help with figuring it out. I appreciate it. A father and son are digging a garden that is 7

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Question 131398: I have been unable to come up with an equation to solve this problem. Could I get some help with figuring it out. I appreciate it. A father and son are digging a garden that is 7 feet long and 5 feet wide. The father, working alone takes 3 hrs. The son working alone takes 4 hrs. If they work together how long would it take?
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
Let t be the time it takes them working together
Father does 1/3 of the job in 1 hr.
Son does 1/4 of the job in 1 hr.
Together they do 1/t of the job in 1 hr.
1/3 + 1/4 = 1/t
4t+3t=12 multiply each side by 12t to eliminate fractions.
7t=12
t=12/7 hrs or 1 hr 43 min (approx.)
.
Ed