An airplane is heading due north at 700 kph, and a wind blows at 60 kph in the direction S 45° E. What is the plane’s ground speed?

The airplane’s velocity is 700 kph north, while the wind has speed 60 kph toward the southeast. The angle between these vectors is 135°, so the ground speed is √(700² + 60² + 2(700)(60)cos 135°) ≈ 658.94 kph. Therefore, the correct choice is 658.94 kph.

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