A rectangular cistern with base 4m by 5m has water to a depth of 6m in it. A solid metal cube with sides 3m is placed into the water. To what level in m does this raise the water in the cistern
Volume of the cube = 3 x 3 x 3 = 27m^3
Volume of the cistern = 4 X 5 x 6 = 120m^3
Total volume of the cistern and added cube = 147m^3
So.....to find the water height, h, with the cube added, we can solve this
4 * 5 * h = 147
20 * h = 147 divide both sides by 20
h = 7.35 m