Which equation represents the total price ($p$) paid when buying books ($b$) that cost $3.99 each? How much do 13 books cost?
A) $b=3.99 p ; $51.87
B) $p=3.99 b ; $0.31
C) $p=3.99 b ; $51.87
D) $b=3.99 c, $51.87
Answer (1)
The total price p is calculated by multiplying the cost per book ($3.99) by the number of books b .
The equation representing the total price is p = 3.99 b .
To find the cost of 13 books, substitute b = 13 into the equation: p = 3.99 × 13 .
The total cost of 13 books is $51.87 .
Explanation
Understanding the Problem We are given that each book costs $3.99, and we want to find the equation that represents the total price ( p ) when buying b books. We also want to calculate the total cost of 13 books.
Finding the Equation The total price p is the cost per book multiplied by the number of books b . Therefore, the equation is: p = 3.99 × b
Substituting the Value of b Now, we need to find the total cost of 13 books. We substitute b = 13 into the equation: p = 3.99 × 13
Calculating the Total Cost Calculating the total cost: p = 3.99 × 13 = 51.87
Finding the Correct Option The equation that represents the total price is p = 3.99 b , and the total cost of 13 books is $51.87. Comparing this with the given options, we find that option C matches our result.
Final Answer Therefore, the correct answer is C) $p=3.99 b ; $ 51.87
Examples
Imagine you're planning a class trip to a museum, and each student needs a guidebook that costs $3.99. This problem helps you calculate the total cost for all the guidebooks based on the number of students attending. Understanding how to calculate total costs based on unit prices is useful in many real-life situations, such as budgeting for groceries, calculating the cost of materials for a project, or determining the revenue from selling a certain number of items. This simple multiplication ensures accurate financial planning and decision-making.
