Question

A 3 kg weight is placed upon a spring so that it hangs downward 12 centimeters. How far would the spring stretch if a 4 kg weight were placed upon it?
Henry
k = 3kg/12cm = 0.25 kg/cm.

d = 4kg * 1cm/0.25kg = 16 cm.

Or
d = (4kg/3kg) * 12cm = 16 cm.