Chapter 11.4, Problem 50STP

To determine

What is the cost in dollars of $36$ CDs?

Answer to Problem 50STP

Option $\boxed{A}$ is correct.

Explanation of Solution

Given information:

The cost of $4$ CDs is $d$ dollars. At this rate, what is the cost in dollars of $36$ CDs?

  $A\left(9d\right)$$D\left(\frac{d}{36}\right)$

  $B\left(144d\right)$$E\left(\frac{36}{d}\right)$

  $C\left(\frac{9d}{4}\right)$

Calculation:

Consider the cost of $4$ CDs is $d$ dollars.

By unitary method,

The cost of each CD in dollars is, $\frac{d}{4}$

Cost of $36$ CDs is $\frac{d}{4}\times 36=9d$

Hence, correct option is $\boxed{A}$ .