2:4

The ratio 2:4 can be simplified. To do this, you divide both numbers by their greatest common divisor (GCD). In this case, the GCD of 2 and 4 is 2.

So, when you simplify 2:4:

\[ \frac{2 \div 2}{4 \div 2} = \frac{1}{2} \]

Therefore, the simplified ratio is 1:2. If you have any other questions or need further assistance, feel free to ask!