So, I didn't quite understand your question clearly, but I'll try my best to answer it.
So, the first question is quite simple: Did the runner have a % decrease in his time or an increase.
Well, 7:45 is minor than 5:51. So, his time decreased.
2nd question:
The percent of change. Well, first things first 7:45 has 2 different units, wich are minutes and seconds, I suppose. Same goes for 5:51.
So let's put everything in seconds. multiply both the 7 and 5 for 60(for every minute has 60 seconds.)
That means:
7*60= 420+45 = 465.
5*60=300+51=351.
Now, let's do the math itself:
465 -> 100%
351 -> x%
Is equal to about 75,5%
How much did it decrease then?
(75,5-100)%= 24,5%, approximately
a constant of proportionality is a number you have to multiply x by to get y.
y=kx is the equation that expresses the proportionality of x and y
the constant of proportionality is k, so k=-5
I would go withhh c but I am not 100% sure
Given:
hours parking charge
4 5.50
7 7.75
7 - 4 = 3 hours
7.75 - 5.50 = 2.25
2.25 / 3 = 0.75
0.75 is the change in amount for every hour spent. It is the variable unit rate
4 hours is 5.50.
Cost of parking for 3 hours is: 5.50 - 0.75 = 4.75
0.75 x 4 hours = 3
5.50 - 3 = 2.5 fixed charge.
total parking charge: y = 2.50 + 0.75x
