PSAT Math Multiple-Choice Question 653: Answer and Explanation

Question: 653

A restaurant charges a $5 standard delivery fee plus a 15% tip on the amount of the bill before the delivery fee. Which of these expressions would model the total cost to have x dollars worth of food delivered?

• A. 0.15x + 5
• B. 1.15x + 5
• C. 5x + 15
• D. 15x + 5

Correct Answer: B

Explanation:

(B) Think of this as 3 separate charges. Let's call x the cost of the food. That's the first charge. Then there's a tip charge that is 15% of the cost of food. The 15% tip charge can be expressed as 0.15x since x is the cost of food. Finally, there's a $5 flat fee delivery charge that doesn't depend on the cost of the food. Therefore, the cost can be represented by:

C = x + 0.15x + 5

Combining like terms gives:

C = 1.15x + 5

Choice (B) is the correct answer.