Let |q| = 5 at an angle of 45° and |r| = 16 at an angle of 300°. What is |q – r|?

The angle between the vectors is 300° − 45° = 255°. By the law of cosines, |q − r|² = 5² + 16² − 2(5)(16)cos(255°) ≈ 322.4, so |q − r| ≈ 17.96. Rounded to one decimal place, this is 18.0, choice D.

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