Question

How do compute ratios like this like 1/4miles Sebastian runs in 1.6 minutes. How long did it take him to run one mile

Answer 1

It's easier to write if you convert 1/4 into 0.25.

$\frac{0.25mi}{1.6min} = \frac{1mi}{xmin}$

Then you use algebra to find that he ran the mile in 6.4 minutes.

Answer 2

There are four 1/4 miles in a mile. 
4*1.6 = 6.4