If we start with 48 atoms of a radioactive substance, how many would remain after one half-life?

One half-life produces (1/2) of the decaying substance.

There would still be  48  atoms.  But  24  would have thrown off
particles from their nucleuses, and only  24  would still be radioactive.

Well the magnitude of its acceleration related to that car starts with the oil change like when you have to change the oil in your car you have to make sure that your precious car is starting really propley and very well