The expression "two fifths of a number" can be translated into a mathematical expression as:

$\frac{2}{5} \times x$

or simply

$\frac{2}{5}x$

where $x$ represents the number.

Would you like further details or have any questions?

Here are 5 related questions to explore:

1. How would you represent "three quarters of a number" in a mathematical expression?
2. If the number $x$ is 10, what is two-fifths of that number?
3. How do you express "a third of a number" mathematically?
4. Can you solve for $x$ if $\frac{2}{5}x = 8$?
5. How would you describe "four-fifths of a number" in mathematical terms?

Tip: When translating phrases to mathematical expressions, identifying keywords like "of," "times," or "per" can help determine the correct mathematical operation.