Hello!
The answer is:
The will paint the same fence at the same time in 2.67 hours.
Why?
From the statement we know that Shawna can paint a fence in 8 hours while Kevin can paint the same in 4 hours, and we are asked to calculate how long will it take them to paint the fence working together, so, calculating we have:
For Shawna, we have:
[tex]ShawnaRate=\frac{FencePainted}{TimeToPaint}\\\\ShawnaRate=\frac{1fence}{8hours}[/tex]
For Kevin, we have:
[tex]KevinRate=\frac{FencePainted}{TimeToPaint}\\\\KevinRate=\frac{1fence}{4hours}[/tex]
So, the combined work for both Shawna and Kevin will be:
[tex]CombinedWorkRate=\frac{1fence}{8hours} +\frac{1fence}{4hours}\\\\CombinedWorkRate=\frac{4fence.hours+8fence.hours}{32hours^{2}}\\ \\CombinedWorkRate=\frac{12fence.hours}{32hours^{2}}\\\\CombinedWorkRate=\frac{12fence.hours}{32hours^{2}}=\frac{3fence}{8hours}[/tex]
Now, if the want to paint the same fence at the same time, we can calculate it by the following way:
[tex]\frac{3fence}{8hours}=\frac{1fence}{x(hours)}\\\\x=1fence*\frac{8hours}{3fence}=2.67hours[/tex]
Hence, the will paint the same fence at the same time in 2.67 hours.
Have a nice day!
