The inverse of multiplication is division. To invert 100x you use x/100 or x(1/100). 1% can be written as 0.01x, 0.01 in fractional form is 1/100. So yeah, "100 times slower" is the inverse of "100 times faster", and if "100 times faster" is 100x, then "100 times slower" would be x/100, or 1%.