To find the original price of the dress, we can use the formula for calculating the sale price based on the original price and the discount percentage.
Let X be the original price of the dress. Since the dress was on sale for 10% off, Kate paid 90% of the original price. We can express this relationship with the equation:
0.90 * X = $27
To find X, divide both sides of the equation by 0.90:
X = $27 / 0.90
X = $30
Therefore, the original price of the dress was $30.