Question 668387: At the start of the School trip to Washington DC the tour bus has 40 gallons of gasoline in the fuel tank. Each hour the bus uses 7 gallons of gasoline. The bus will stop for gas when there are 10 gallons left.
A. Make a table to show how many gallons of gas are remaining in the fuel tank after each hour.
B. Write and solve an equation to find how many hours will pass before the bus will have to stop for gasoline.
Answer we came up with for part A.
gallons/ Hours
40/0; 33/1; 26/2; 19/3; 12/4; 5/5
we took the total gallons (40) and subtracted 7 gallons for each hour to get this chart.
Part B. we are not sure how to write the equation.
This was our attempt: 40 gallons - 7/60 = 10 gallons
7/60 represents the 7 gallons used each hour. 60 = min per hour.
But we are not able to get a correct answer. So what are we doing wrong?
Can you help please?
Found 2 solutions by ankor@dixie-net.com, MathTherapy:
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! At the start of the School trip to Washington DC the tour bus has 40 gallons of gasoline in the fuel tank. Each hour the bus uses 7 gallons of gasoline. The bus will stop for gas when there are 10 gallons left.
A. Make a table to show how many gallons of gas are remaining in the fuel tank after each hour.
B. Write and solve an equation to find how many hours will pass before the bus will have to stop for gasoline.
Answer we came up with for part A.
gallons/ Hours
40/0; 33/1; 26/2; 19/3; 12/4; 5/5
we took the total gallons (40) and subtracted 7 gallons for each hour to get this chart.
Part B. we are not sure how to write the equation.
let h = no. of hours
40 - 7h = 10
solve
-7h = 10 - 40
-7h = -30
h = 
h = +4.3 hrs
Answer by MathTherapy(10552)  (Show Source):
You can put this solution on YOUR website! At the start of the School trip to Washington DC the tour bus has 40 gallons of gasoline in the fuel tank. Each hour the bus uses 7 gallons of gasoline. The bus will stop for gas when there are 10 gallons left.
A. Make a table to show how many gallons of gas are remaining in the fuel tank after each hour.
B. Write and solve an equation to find how many hours will pass before the bus will have to stop for gasoline.
Answer we came up with for part A.
gallons/ Hours
40/0; 33/1; 26/2; 19/3; 12/4; 5/5
we took the total gallons (40) and subtracted 7 gallons for each hour to get this chart.
Part B. we are not sure how to write the equation.
This was our attempt: 40 gallons - 7/60 = 10 gallons
7/60 represents the 7 gallons used each hour. 60 = min per hour.
But we are not able to get a correct answer. So what are we doing wrong?
Can you help please?
For every hour, 7 gallons of gas is expended. Therefore, we have a slope of - 7, or we can use two of the points, (0, 40) and (1, 33) to determine the slope
(0, 40) and (1, 33)
m, or slope =  ------  , or - 7
y – 40 = - 7(x – 0)
y – 40 = - 7x
y = - 7x + 40
P(h) = - 7h + 40 (Equation needed), with P being petrol remaining after h (hours)
10 = - 7h + 40 ------ Hours (10) that will pass before the bus has to stop
7h = 40 – 10
7h = 30
h, or amount of hours before bus has to stop =  , or  , or about 4 hours, 17 minutes
It can be seen from the table created, that at the 4-hour juncture, only 12 gallons remain, meaning that it can travel a little more than 4 hours before having to stop to gas up.
Send comments and “thank-yous” to “D” at MathMadEzy@aol.com
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