The LessonA percentage is a part of a whole. It expresses a part of a whole number as parts out of 100. A percentage is shown by the symbol % (said as "percent").
Dictionary DefinitionThe Merriam-Webster dictionary defines a percentage as "a part of a whole expressed in hundredths."
A Real Example of a PercentageA percentage is written as a number followed by the percentage symbol %:
This is 20% (said as "20 percent"). It means 20 parts out of 100.
A Real Example of What a Percentage MeansImagine you were given 20% in a mathematics exam. You would have got 20 out of every 100 marks.
- If there were 100 marks, you would have got 20 marks.
- If there were 200 marks, you would have got 40 marks.
- If there were 50 marks, you would have got 10 marks.
Visualizing PercentagesA percentage shows how many parts out of a 100. A grid with 100 squares is a useful way of visualizing percentages. In the grid below, 20 out of 100 squares are colored blue. 20% of the squares are blue.
Lesson SlidesThe slider below shows some more examples of visualizing percentages using a grid of 100 squares.
What's in a Name?"Per cent" comes from the Latin "per centum", meaning "by the hundred". The word "cent" appears in many contexts. In currencies, a hundredth of a US dollar is a cent. A hundredth of a Euro is also a cent. A hundred years is called a century and a hundred year anniversary is a centennial.
Other Types of Fractional NumbersPercentages express a part of a whole. There are other ways of expressing parts of a whole: For example:
- A fraction: 1/2
- A decimal: 0.5
- A negative exponent: 2−1
- A percentage: 50%
- A ratio: 1:2