1. Help with an exercise

Three electricians can individually complete a certain job in 4, 5 and 10 hours. The fractional part of the job that the two faster electricians can finish in one hour is how much greater than the fractional part of the job that the two slower electricians can finish in one hour?

thanks in advance for the explanation.

2. First, let's look at each of the electrician's completion rates per hour: $\displaystyle \frac{1}{4}$, $\displaystyle \frac{1}{5}$, and $\displaystyle \frac{1}{10}$.

So, the two faster electricians finish $\displaystyle (\frac{1}{4} + \frac{1}{5})$ each hour, and the two slower electricians finish $\displaystyle (\frac{1}{5} + \frac{1}{10})$ in an hour.

Therefore, the two faster electricians are faster by
$\displaystyle (\frac{1}{4} + \frac{1}{5}) - (\frac{1}{5} + \frac{1}{10})$

$\displaystyle (\frac{1}{4}) - (\frac{1}{10})$

$\displaystyle (\frac{5}{20}) - (\frac{2}{20})$

$\displaystyle \frac{3}{20}$

3. Thanks Henderson

This is the first time that I use this forum.

Thanks a lot Henderson for the fast answer.