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,
![\text{ 6 miles : 45 minutes = 4 miles : x}](https://img.qammunity.org/2023/formulas/mathematics/college/k903blclxfzj9l3qza54ufbv9iq9o4lcbu.png)
Where,
x = time he would take to run 4 miles.
![\text{ 6 miles : 45 minutes = 4 miles : x }\rightarrow\text{ }\frac{\text{6 miles}}{45\text{ minutes}}=\frac{4\text{ miles}}{x}_{}](https://img.qammunity.org/2023/formulas/mathematics/college/5wzlavnlzkp92tvp599qlepwz9f73nedht.png)
![\frac{\text{6 miles}}{45\text{ minutes}}=\frac{4\text{ miles}}{x}](https://img.qammunity.org/2023/formulas/mathematics/college/jr14smgmc0vcvqrq8k4hyttzblpchuvivn.png)
![(6\text{ miles)(x) = (4 miles)(45 minutes)}](https://img.qammunity.org/2023/formulas/mathematics/college/lb3vpnis8dlgsaiuykgee8dkykovr593ot.png)
![\text{x = }\frac{\text{4 (miles) x 45 minutes}}{6\text{ (miles)}}](https://img.qammunity.org/2023/formulas/mathematics/college/6raogmto8iw2avw0owanh5f8nnib29m3wv.png)
![\text{x = }\frac{\text{180 minutes}}{6\text{ }}](https://img.qammunity.org/2023/formulas/mathematics/college/8k6ilpe5llv8be4nfw85utmyb53ncqxry9.png)
![\text{ x =30 minutes}](https://img.qammunity.org/2023/formulas/mathematics/college/aznlb5cyut0z918lwb3n96c397go350iee.png)
Therefore, it'll take 30 minutes for Hans to run 4 miles.