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I know for this question that a) and b) are correct, but c) is not. Not exactly what it means by "the ratio" so I just took the length of both U and V and divided it.

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    You did the work correctly, but look more carefully. They are looking for $||v|| / ||u||$ and you gave them $||u|| / ||v||$. (You should get $\sqrt{54} / \sqrt{6} = 3$) – 2017-01-24

1 Answers 1

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Your first two calculations are correct. However, on the third one, you gave the value of $\frac{\|u\|}{||v||}$ instead of $\frac{\|v\|}{\|u\|}$.

Therefore, it should be:

$\|u\|=\sqrt{(-1)^2+(2)^2+(1)^2}=\sqrt{6}$

$\|v\|=\sqrt{(3)^2+(3)^2+(6)^2}=\sqrt{54}$

Giving you the answer:

$$\frac{\|v\|}{\|u\|}=\sqrt{\frac{54}{6}}=3$$

Which is the reciprocal of the answer you have written.