How do you determine impressions when given cost and CPM?

To determine impressions when given cost and CPM (Cost Per Mille, or cost per thousand impressions), the correct formula is to divide the total cost by the CPM and then multiply by 1000. This is because CPM tells you how much it costs to reach one thousand impressions. Therefore, by taking the total cost and dividing it by the CPM, you find out how many thousands of impressions you have purchased. Multiplying that result by 1000 converts the value back into actual impressions.

For example, if the cost of an ad is $500 and the CPM is $10, using the formula would yield:

Impressions = (500 / 10) x 1000 = 50,000 impressions.

This makes option B the most accurate method for calculating impressions based on cost and CPM.