You fill your car with 15 gallons of gas at a cost of $45. Using fractional notation, how do you write a proportion that shows how much 5 gallons of gas will cost? Use x to represent the unknown cost.
A. 15/45 = x/5
B. 15/x = 45/5
C. 15 : 45 :: x : 5
D. 15/45 = 5/x
A. 15/45 = x/5 is the correct proportion to use.
To solve for x, cross-multiply and simplify:
15 * 5 = 45 * x
75 = 45x
x = 75/45
x = 5/3, which in decimal form is approximately $1.67
Therefore, 5 gallons of gas will cost approximately $1.67.