The airplane's speed relative to the ground is
                   √ (100² + 25²)
                 = √ (10,000 + 625)
                 = √ 10,625
                 =   103.08 km/hr .
The angle of its velocity north of west is
the angle whose tangent is (25/100)
             arctan(25/100) = 14° north of west .
                       (bearing = 284°)