Chapter 4, Problem 11STP

(a)

To determine

To find: the equation for the time J needs to refuel

Answer to Problem 11STP

The required equation is $19-h=3$

Explanation of Solution

Given:

J has 19 gallons of gasoline

She uses 1 gallon every 30 minutes,

Calculation:

Let h represent the number of half-hours.

Because Jasmine's car uses 1 gallon every 30 minutes, or half-hour, subtract h from the number of gallons initially in the tank.

She wants to refuel, when she has 3 gallons left so $19-h=3$ represents the amount of gasoline in her car's tank after h half-hours.

Jasmine plans to stop and refuel when there are 3 gallons of gasoline left in her tank. For that expression is,

  $19-h=3$

Conclusion:

Therefore, the required equation is $19-h=3$

(b)

To determine

To find: the time J needs to refuel

Answer to Problem 11STP

After 16 half-hours, or 8 hours, Jasmine will have to refuel.

Explanation of Solution

Given:

J has 19 gallons of gasoline

She uses 1 gallon every 30 minutes,

Calculation:

The equation found from part a is $19-h=3$

Making like terms together,

  $\begin{array}{l}19-3=h\hfill \\ h=16\hfill \end{array}$

Conclusion:

Hence, after 16 half-hours, or 8 hours, Jasmine will have to refuel.