What are three disadvantages of case studies

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?

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?

Arock displaces 1.65 l of water. the volume of the rock is: a: 1,650 cm³ b: 165.0 cm³ c: 16.50 cm³ d: 0.165 cm³