If you were mature, you'd handle the truth about your age in an honest way, since you'd have the wisdom to know there really isn't any other way.
Reach down deep... locate your balls... and tell the truth.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen