Our spreadsheet

Once you've downloaded our spreadsheet, open the file in Excel or another spreadsheet application. Here, we have two main columns: one for the item name, and another for the item price. There's also a formula in cell B5 that calculates the original total cost of the items: =SUM(B2:B4)

What are we trying to figure out?

Let's think about the problem we're trying to solve. We want to know the total cost after the discount. A discount is a percentage of the original price. In this example, the discount is 15% of the original total.

To make this problem easier to solve with a spreadsheet, we'll break it down into two steps:

1. Find the discount, which is 15% of $78.77.
2. Subtract that value from the original total to find the final cost.

Step 1: Find the discount

We know that we need a formula that will calculate 15% of $78.77. Whenever you see the phrase "of something" in a percentage problem, it's a hint that you need to multiply. So we'll need to multiply $78.77 by 15% to find the discount. When you're using percentages within formulas, you'll want to write them as decimals.

Excellent! Now that we know how to write 15% as a decimal, we're ready to write our formula:

=B5*0.15

We'll type this formula in cell B6 and then press Enter:

And here's our answer: The discount is $11.82.

Step 2: Subtract the discount from the original total

Now that we've calculated our discount, we'll subtract that value from the original total. Here's our formula:

=B5-B6

We'll type this formula in cell B7 and press Enter:

The final price after the discount will be $66.95.

Bonus Section

In the example above, we found the discount and then subtracted that from the original total. To make this simpler, we broke the problem down into two smaller steps. However, if you're comfortable working with percentage problems, we could have found the same answer with only one formula.

Can you figure out which formula we could have used instead? Here's a hint: Because we know we'll get 15% off, you could also say the final cost would be 85% of the original total.