The price of one gallon of unleaded gasoline at the pump rea

The price of one gallon of unleaded gasoline at the pump reached $1.73 on January 1st of 2004 and continued to rise at the rate of 4 cents per month for the next nine months. Express the price of one gallon of unleaded gasoline as a function of time for the period starting January 2004. What was the price of 13 gallons of gas on June 1st 2004? On September 1st 2004?

Let P equal the price per gallon and x equal the number of months since January 2004. Express the price of one gallon of unleaded gasoline as a function of time for the period starting January 2004.

Solution

Initial price per gallon = $1.73

rise in price every month = 4 cents = $0.04

So the equation should be

P = (price rise) *x + initial price

where P is price per gallon

and x is number of months

So

P= 0.04x +1.73

What was the price of 13 gallons of gas on June 1st 2004?

price per gallon on june 1st 2004 , that is after january actually it is sixth month but , the price rise started from next month So it means x=5

So P= 0.04(5) + 1.73 = 0.20 +1.73 = $1.93

On September 1st 2004?

means 8 months after january

So

P= 0.04(8) + 1.73

= 0.32+1.73

= $2.05