Percentage disc
About this app
Connect percentages, fractions, decimals and sectors of a circle. Explore how the base amount changes the result and practise all three percentage problems.
Base, rate and part
Percent means “per hundred”: 25 % = 25/100 = 1/4 = 0.25. Percentage problems link three quantities. The base value G is the whole (100 %), the rate p is the share, and the percentage value W is the part. They satisfy W = G · p / 100, which can be rearranged to p = W / G · 100 or G = W / p · 100, depending on what is unknown.
What the app shows
A disc shows the rate as a filled sector, with the same share written below as a percentage, fraction and decimal. A bar represents the base value and marks the percentage value. A switch selects whether W, p or G is unknown; the formula is evaluated with the current numbers, and the value of 1 % of the base is shown as well.
Try it yourself
Keep the rate fixed and make the base larger: the sector stays the same while the marked part of the bar grows. 20 % of 50 is 10, 20 % of 200 is 40. A percentage alone is not a fixed amount; it always refers to a base. Then switch the unknown quantity and see how the same formula is rearranged.
Frequently asked questions
- How do you calculate a percentage of a number?
- Multiply the number by the rate and divide by 100: 15 % of 80 is 80 · 15 / 100 = 12. You can also find 1 % first (here 0.8) and multiply by the rate.
- How do you find the whole when you know the part and the percentage?
- Use G = W / p · 100. If 12 is 15 % of the whole, then G = 12 / 15 · 100 = 80. Working via 1 % gives the same result: 15 % is 12, 1 % is 0.8, 100 % is 80.
- How do you convert a percentage to a fraction or decimal?
- Divide by 100: 25 % = 25/100 = 0.25, which simplifies to 1/4. To go back, multiply the decimal by 100, for example 0.4 = 40 %.
- What does the percent disc app show?
- It shows one share as percent, fraction, decimal and pie sector and links it to a base value bar. You can switch between the three basic percentage problems and let the app work through your own numbers.
Subject: School mathematics (Gymnasium)
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