Answer:
A) The amount of gas they bought on each coast;
East Coast = 35 gallons
Mid-US = 100 gallons
West Coast = 15 gallons
B) The amount of gas they bought on each coast on the return journey;
East Coast = 37 gallons
Mid-US = 116 gallons
West Coast = 21 gallons
Step-by-step explanation:
Complete Question
Maxis taking a cross-country road trip. Gas prices vary as the friends travel across the US from $4 dollars per gallon on the east coast to $3 in the mid-US, to $5 on the west coast.
(a) If they used twice as much gas in the mid-US than on either coast combined, and they spend $515 on gas to purchased 150 gallons of gas, how many gallons of gas did they buy at each price?
The answer to this question is East Coast - 35 gal, Mid-US - 100 gal, West Coast - 15 gal.
(b) On their way back they had more baggage in the car and spend $601 for 174 gallons of gas. Based on the same ratio as in Part (a), how many gallons of gas did they buy at each price? I don't know the answer to this one
Solution
Let the amount of fuel bought on the east coast = x gallons
Let the amount of fuel bought on the mid-coast = y gallons
Let the amount of fuel bought on the west coast = z gallons
a) - They used twice as much gas in the mid-US than on either coast combined
y = 2(x + z) = 2x + 2z (eqn 1)
- They spend $515 on gas to purchase 150 gallons of gas.
Total gallons purchased = x + y + z = 150
Total amount spent = 4x + 3y + 5z = 515
From eqn 1, y = 2x + 2z, inserting this value for y in the 2 other equations
x + y + z = x + 2x + 2z + z = 150
3x + 3z = 150
Divide through by 3
x + z = 50 (eqn *)
4x + 3y + 5z = 4x + 3(2x + 2z) + 5z = 515
4x + 6x + 6z + 5z = 515
10x + 11z = 515 (eqn **)
x + z = 50
10x + 11z = 515
Solving the simultaneous equation,
x = 35 gallons
z = 15 gallons
y = 2x + 2z = 2(35 + 15) = 100 gallons
B) On the return journey, the ratio between x, y and z is still the same, but the total gallons and total amount spent is now different.
They used twice as much gas in the mid-US than on either coast combined
y = 2(x + z) = 2x + 2z (eqn 1)
- They spend $601 on gas to purchase 174 gallons of gas.
Total gallons purchased = x + y + z = 174
Total amount spent = 4x + 3y + 5z = 601
From eqn 1, y = 2x + 2z, inserting this value for y in the 2 other equations
x + y + z = x + 2x + 2z + z = 174
3x + 3z = 174
Divide through by 3
x + z = 58 (eqn *)
4x + 3y + 5z = 4x + 3(2x + 2z) + 5z = 601
4x + 6x + 6z + 5z = 601
10x + 11z = 601 (eqn **)
x + z = 58
10x + 11z = 601
Solving the simultaneous equation,
x = 37 gallons
z = 21 gallons
y = 2x + 2z = 2(37 + 21) = 116 gallons
Hope this Helps!!!
