Using proportions, it is found that it would take 6.4 days for 8 men to dig a trench of 360 meters long working at the same rate.
A proportion is a fraction of a total amount, and the measures are related using a rule of three.
In this problem, the rule of three is given as follows:
8 days - 15 men - 240 meters
x days - 18 men - 360 meters
The number of men is inverse proportional to the number of days, hence we divide 18 by 15 instead of 15 by 18, then:
[tex]\frac{8}{x} = \frac{18}{15} \times \frac{24}{36}[/tex]
[tex]\frac{8}{x} = \frac{6}{5} \times \frac{4}{6}[/tex]
[tex]\frac{8}{x} = \frac{5}{4}[/tex]
Applying cross multiplication:
5x = 32.
x = 32/5
x = 6.4 days.
More can be learned about proportions at https://brainly.com/question/24372153
#SPJ1