Scalar Multiplication, why do I keep getting this bizarre result? I have two vectors, u and v
u = [2/5,-1,1/5]
v = [-1,5/2, -1/2] 

I need to prove that they are Scalar of one another, and in such a way that  u = kv

k being the scalar variable.

The intuitive method would be to look at it and see what happens when you multiply 2/5 by v and suddenly it equals u.

However, I want to do things by the book and FIND the scalar multiple using math.

So, I do the standard formula (u*v)/|v|

However, I keep getting -3/(sqrt(30))/2

Which doesn't line up with the actual result. 

What I have tried:

u*v is just a dot product, right? So that ends up giving you -(2/5) + -(5/2) + -(1/10) which ends up being -30/10 = -3.

Now the denominator which is magnitude v or |v| which is sqrt((-1)^2 + (5/2)^2 + (-1/5)^2) which netted me sqrt(30)/2, this isn't the result that I need or that mathlab says is correct, a little help would go a long way here.
You say that you want to "find the scalar using math."

$u = (u_1,u_2, u_3) , v = (v_1,v_2, v_3)$

It is given that one vector is a scalar multiple of the other.

$u = \lambda v\\
\lambda = \frac {u_1}{v_1} = \frac {u_2}{v_2} = \frac {u_3}{v_3}$

Is a perfectly valid approach "using math"

If "by the book," means using the dot product...

$u = \lambda v\\
u\cdot v = \lambda v\cdot v = \lambda \|v\|^2\\
\lambda = \frac {u\cdot v}{\|v\|^2}$

$\lambda = \frac {-\frac {2}{5} - \frac {5}{2} - \frac {1}{10}}{1 + \frac {25}{4} + \frac 14} = -\frac {2}{5}$
Multiplying the first vector by the scalar $-\frac{5}{2}$ yields the second vector.

$u = kv$

So $$k = \frac{-1}{(\frac{2}{5})} = \frac{(\frac{5}{2})}{-1} = \frac{-(\frac{1}{2})}{(\frac{1}{5})} = -\frac{5}{2}$$