To solve the multiplication sentence \( 775.1 \cdot 1 = s \), we can use the property of multiplication that states any number multiplied by 1 is equal to itself.
Therefore: \[ s = 775.1 \cdot 1 = 775.1 \]
The value of \( s \) that makes the multiplication sentence true is: \[ \boxed{775.1} \]