Answer:
The new radius of the trajectory of the particle is four times the previous radius
Explanation:
In order to know what is the radius of the trajectory of the charged particle, if its speed is four times as fast, you take into account the following formula, which describes the radius of a charged particle in a magnetic field:
(1)
If the speed of the particle is for time as fast, that is, v' = 4v, you obtain, in the equation (1):

The new radius of the trajectory of the particle is four times the previous radius
Because the position depends on the amount of time that has passed.
Acceleration = (change in velocity) / (time for the change) .
They may have had the same change in velocity, but if the changes
happened in different lengths of time, then their accelerations were
not the same.
At a given moment in time, the instantaneous speed can be thought of as the magnitude of instantaneous velocity.
Instantaneous speed is the magnitude of the instantaneous velocity, the instantaneous velocity has direction but the instantaneous speed does not have any direction. Hence, the instantaneous speed has the same value as that of the magnitude of the instantaneous velocity. It doesn't have any direction.