Percentages as Fractions
Define percentage as 'number of parts per hundred'; interpret percentages and percentage changes as a fraction or a decimal; express one quantity as a percentage of another; compare quantities using percentages; work with percentages greater than 100%
What a learner can do afterwards
- Convert fluently between percentages, fractions, and decimals
- Express one quantity as a percentage of another
- Calculate percentage increases and decreases and interpret percentages greater than 100%
The lesson
Percent means 'per hundred.' The word comes from 'cent,' the same root as century, which is 100 years. So 40% means 40 out of every 100.
A percentage is just a fraction with 100 on the bottom. 25% is 25/100, which simplifies to 1/4. As a decimal, 25% is 0.25. The fraction, the decimal, and the percentage are the same amount written three different ways.
Zara answers a 10-question quiz and gets 9 right. 9 out of 10 is 9/10. Multiply the top and bottom by 10 to get 90/100, so Zara scored 90%.
Percentages can go over 100%. If a jacket now costs 120% of its old price, that means the new price is the whole old price (100%) plus another 20% on top, so it costs more than before.
A percentage is a fraction out of 100, and the same amount can be written as a fraction, a decimal, or a percentage.
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.