A smart phone manufacturer uses 10 ounces of gold circuitry to make 5,200 smart phones. If they made 7,800 smart phones last month and gold is valued at $1,300 per ounce, what is the value of gold used last month?

$19,500

Step-by-step explanation:

In this question, the first thing we do

Is to calculate the amount of gold that was used in making 7,800 smartphones. We proceed as follows:

Firstly, 10 ounces made 5,200 smartphones, then x ounces will make 7,800 smartphones

Thus 10 * 7,800 = 5,200 * x

x = 78,000/5200 = 15 ounces

This means that 7,800 smartphones were made using 15 ounces of gold

Now, we know that the value of an ounce is $1,300. Thus, the value of 15 ounces would be 15 * 1,300 = $19,500