Digital ACT Math Practice Question #1205
Test your problem-solving accuracy on this official-caliber item. Select an answer choice to check your reasoning instantly.
Perpendicular dot product: $3k + (-4)(6) = 0 \implies 3k = 24 \implies k = 8$. Takes under 5 seconds.
Two nonzero vectors are perpendicular if and only if their dot product equals zero: $\mathbf{u} \cdot \mathbf{v} = 0$. $$\mathbf{u} \cdot \mathbf{v} = (3)(k) + (-4)(6) = 3k - 24 = 0 \implies 3k = 24 \implies k = 8.$$...
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