SAT Math Multiple Choice Question 426: Answer and Explanation
6. At the grocery store, Gigi buys apples, a magazine, and a gallon of milk. The apples are priced per pound. In her state, there is no sales tax on food. If the total cost of her items is given by the function C(p) = 1.89p + 1.07(3.99) + 4.49, then the term 1.07(3.99) most likely represents
- A. the cost of one gallon of milk.
- B. the per-pound cost of the apples.
- C. the cost of the magazine, including tax.
- D. the cost of the magazine, not including tax.
Correct Answer: C
Category: Heart of Algebra / Linear Equations
Strategic Advice: In a real-world scenario, a one-time fee does not depend on the variable and is therefore a constant. A unit rate, however, is always multiplied by the independent variable.
Getting to the Answer: The total cost consists of the gallon of milk (a constant), the per-pound cost of the apples (which depends on the number of pounds), and the cost of the magazine (which is the only taxed item). The constant in the equation is 4.49 and is, therefore, the cost of the gallon of milk; 1.89 is being multiplied by p (the number of pounds), so $1.89 must be the per-pound cost of the apples. That leaves the remaining term, 1.07(3.99), which must be the cost of the magazine ($3.99) plus a 7% sales tax.