To find how long it will take to fill the tank, you can use the idea that every 30 seconds will get you one gallon closer to being full.
This means to fill 50 gallons, you will need 50 groups of 30 seconds.
50 x 30 = 1500 seconds
1500/60 = 25 minutes.
It will take 25 minutes.
You could also think of it as filling 2 gallons every minute. It would take 25 of these.
For this case we have that the original value of the car is:
m dollars
For the following year we have the value is:
((100-15) / (100)) m
Rewriting we have:
((85) / (100)) m
0.85m
Answer:
the value of his car the year after the car is worth m dollars is:
B.f (m) = 0.85m