How would you do this problem?

Question

At the beginning of the year, the price of gasoline is $1.05 per gallon. The price increased $0.05 per gallon each week for the next 5 weeks. The price then decreased $0.07 per gallon for the next 3 weeks. Find the difference between the cost of 10 gallons at the beginning of the year and 10 gallons 8 weeks later. Show your work.

Answer 1

Cost of 10 gallons at beginning of year = 10 gallons x (1.05/gallon) = W

Price per gallon at end of 8 weeks is
1.05 + (5*0.05)+ (3*-.07) = Y
Cost of 10 gallons at end of 8 weeks is 10*Y.

Calculate the difference between Y and W.

Answer 2

$0.05 * 5 = $0.25

$1.05 + $0.25 = $1.30

$0.07 * 3 = $0.21

$1.30 - $0.21 = $1.09

10 * $1.05 = $10.50
10 * $1.09 = $10.90

$10.90 - 10.50 = ??

Answer 3

Thank you. I got $4.60, is that right?

Answer 4

Now I got $0.40, is that right now?

Answer 5

Yes. $0.40 is correct.