Find percentages of a quantity - Find 25% & 50%
Theory
50% of a quantity is one half — divide by \(2\). 25% is one quarter — divide by \(4\). Build 75% by adding the half and the quarter.
A percentage is a part out of \(100\). Two of them turn into very easy fractions.
50% is one half, \(\dfrac{1}{2}\), so \(50\%\) of a quantity means divide it by \(2\).
25% is one quarter, \(\dfrac{1}{4}\), so \(25\%\) of a quantity means divide it by \(4\).
75% is \(50\% + 25\%\): find the half and the quarter, then add them.
The friendly percentages each match a simple fraction and a quick rule.
| Percentage | Fraction | To find it |
|---|---|---|
| 50% | \(\dfrac{1}{2}\) | divide by \(2\) |
| 25% | \(\dfrac{1}{4}\) | divide by \(4\) |
| 75% | \(\dfrac{3}{4}\) | half plus quarter |
| 10% | \(\dfrac{1}{10}\) | divide by \(10\) |
| 100% | \(1\) | the whole amount |
How to find 25% or 50% of a quantity
- Choose the fraction. \(50\%\) is a half; \(25\%\) is a quarter.
- Divide. Divide the quantity by \(2\) for \(50\%\), or by \(4\) for \(25\%\).
- Build 75% if needed. Add the half and the quarter together.
50% is one half, so divide by 2.
| \(48 \div 2\) | \(=\) | \(24\) |
25% is one quarter, so divide by 4.
| \(120 \div 4\) | \(=\) | \(30\) |
75% is 50% plus 25%.
| \(80 \div 2\) | \(=\) | \(40\) |
| \(80 \div 4\) | \(=\) | \(20\) |
| \(40 + 20\) | \(=\) | \(60\) |
So 7 students ride a bike.
| \(28 \div 4\) | \(=\) | \(7\) |
Common pitfalls
Frequently asked questions
How do you find 50% of a number?
Halve it. \(50\%\) is one half, so divide the number by \(2\). For example, \(50\%\) of \(48\) is \(48 \div 2 = 24\).
How do you find 25% of a number?
Take one quarter. \(25\%\) is \(\dfrac{1}{4}\), so divide by \(4\). For example, \(25\%\) of \(120\) is \(120 \div 4 = 30\).
How do you find 75% of a number?
Add 50% and 25%. Find the half and the quarter, then add them. For \(80\): \(40 + 20 = 60\).
Why is 25% the same as dividing by 4?
Because \(25\% = \dfrac{25}{100} = \dfrac{1}{4}\). Finding a quarter of an amount means splitting it into four equal parts, which is dividing by \(4\).
What if half of a number is not whole?
That is fine. Half of an odd number ends in \(.5\), so \(50\%\) of \(7\) is \(3.5\). A decimal answer is still correct.