Example:

1.9.3p327 :002 > speed = 3.0
 => 3.0 
1.9.3p327 :003 > 1.0/speed
 => 0.3333333333333333 
1.9.3p327 :004 > speed = 3
 => 3 
1.9.3p327 :005 > 1.0/speed
 => 0.3333333333333333 
1.9.3p327 :006 > 1/speed 
 => 0 
1.9.3p327 :007 > 


So you wouldn't actually need to .to_f the bruteforce_speed as long as 1.0 is on top.