How is the magnitude of a vector quantity represented?

Two vectors $\overrightarrow{X}$ and $\overrightarrow{Y}$ have equal magnitude. The magnitude of $(\overrightarrow{X}-\overrightarrow{Y})$ is $n$ times the magnitude of $(\overrightarrow{X}+\overrightarrow{Y})$. The angle between $\overrightarrow{X}$ and $\overrightarrow{Y}$ is:

What is the minimum number of coplanar vectors of different magnitudes whose sum can be zero?

What is the minimum number of non-zero vectors in different planes that can be added to give a zero resultant?

If the velocity of the electron in Bohr's first orbit is $2.19 \times 10^6 \text{ m s}^{-1}$, calculate the de Broglie wavelength associated with it. [$h = 6.626 \times 10^{-34} \text{ J s}$ and mass of electron = $9.10938 \times 10^{-31} \text{ kg}$] (in $\text{ pm}$)

Can you associate vectors with $(a)$ the length of a wire bent into a loop,$(b)$ a plane area,$(c)$ a sphere? Explain.