Assume the energy of the electron is 1keV: try to calculate it's velocity.

Assume the magnetic field is 1kG(Gauss)=0.1T(Tesla) and velocity is perpendicular to the magnetic field.

: try to calculate it radius and frequency.

With the above calculated data: try to think of the motion of the electron.

If the velocity of the electron is not perpendicular: assume 1% of velocity is parallel to the magnetic field.

What do you think about the average motion of the electron will be look like?