Final answer:
To find the discount cost of an item during a 30% sale, multiply the original price by the discount rate.
Step-by-step explanation:
To find the discount cost of an item during a 30% sale, you can use the following expression:
Original Price x Discount Rate = Discount Cost
For example, if the original price of an item is $50, the discount cost would be:
$50 x 0.30 = $15
Therefore, the discount cost for that item would be $15.