To solve the inequality \( \sqrt{2n} < 5 \), we can first square both sides to eliminate the square root (keeping in mind that both sides are non-negative):
\[ 2n < 25 \]
Next, divide both sides by 2:
\[ n < 12.5 \]
Now let's check the response options:
- 12.5: This does not satisfy the inequality since \( n \) must be less than 12.5.
- 16: This does not satisfy the inequality since \( 16 \) is greater than \( 12.5 \).
- 18: This does not satisfy the inequality since \( 18 \) is greater than \( 12.5 \).
- 8: This satisfies the inequality since \( 8 < 12.5 \).
Therefore, the value for \( n \) that makes the inequality \( \sqrt{2n} < 5 \) true is 8.