Given:
a.) Hans runs 6 miles in 45 minutes.
To be able to determine how many minutes would he take to run 4 miles, we will be using ratio and proportions.
We get,
[tex]\text{ 6 miles : 45 minutes = 4 miles : x}[/tex]Where,
x = time he would take to run 4 miles.
[tex]\text{ 6 miles : 45 minutes = 4 miles : x }\rightarrow\text{ }\frac{\text{6 miles}}{45\text{ minutes}}=\frac{4\text{ miles}}{x}_{}[/tex][tex]\frac{\text{6 miles}}{45\text{ minutes}}=\frac{4\text{ miles}}{x}[/tex][tex](6\text{ miles)(x) = (4 miles)(45 minutes)}[/tex][tex]\text{x = }\frac{\text{4 (miles) x 45 minutes}}{6\text{ (miles)}}[/tex][tex]\text{x = }\frac{\text{180 minutes}}{6\text{ }}[/tex][tex]\text{ x =30 minutes}[/tex]Therefore, it'll take 30 minutes for Hans to run 4 miles.