Which is the correctly balanced equation for the reaction of rust, fe2o3, and hydrochloric acid, hcl? a. fe2o3 + hcl → fecl3 + h2o b. fe2o3 +3 hcl → 2 fecl3 + h2o c. fe2o3 + 6 hcl → 2 fecl3 + 3 h2o d. fe2o3 + 3 hcl → 2 fecl3 + 3 h2o

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?