# Lesson 5: Square root. Percent

In this lesson we are discussing two topics: square root of a number and percent.

A square root of a number is a number that has been squared to get the number under the square root.

For example, the √4 is 2, because 2 x 2 = 4.

Watch the video lesson to see the examples and learn why we cannot take a square root of a negative number.

We have already discussed the concept of percent in our previous lessons. However, since it is a very commonly used concept, we will go over it again in more detail.

In this lesson you will learn the general formula for finding the percent of a number. You will see how to use proportions in order to calculate percent.

Together, we will go over some real life problems with percentages.

For additional explanation and math practice, check out the note and workbook.