Answer:
1 hour (60 minutes)
Step-by-step explanation:
If his speed remains the same, that means that this is a linear relationship. y increases at the same rate as x increases. Direct variation and all of that. Because this is a linear relationship, it can be solved using proportions. Set up the given info in a ratio with miles on the top and minutes on the bottom:
[tex]\frac{miles}{minutes}:\frac{4}{20}[/tex]
Now we want to know how long (unknown number of minutes) it will take him to go 12 miles. Keep miles with miles and minutes with minutes:
[tex]\frac{miles}{minutes}:\frac{4}{20}[/tex]=[tex]\frac{12}{x}[/tex]
We can cross multiply now to get 4x = 12(20) and 4x = 240. That means that x=60. It will take him 60 minutes (1 hour) to go 12 miles.
