Answer:
26.67 hours or 26 hours and 40 minutes.
Step-by-step explanation:
To find out how long will it take for Joe and Bill to finish building the wall together, first find their individual work rates in feet per hour:
Bill:
[tex]B = \frac{10\ ft}{4 h} \\B = 2.5\frac{\ ft}{h}[/tex]
Joe:
[tex]B = \frac{10\ ft}{5 h} \\B = 2.0\frac{\ ft}{h}[/tex]
Their combined work rate is:
[tex]W =J+B\\W = 2.5\frac{\ ft}{h}+2.0\frac{\ ft}{h}\\W=4.5\frac{\ ft}{h}[/tex]
Then, divide the total size of the wall by their work rate to find the time spent to finish it:
[tex]t = \frac{120\ ft}{2.5\frac{\ ft}{h}} \\t= 26.67\ h[/tex]
