A layer of water Ax m thick which lies x m above the bottom of the tank will be rectangular with length 8 m. Using similar triangles, we can see that it will have width x m. | 3 m + 3 i 3 m 3 8 m Step 2 The mass of the layer of water is approximately equal to its density (1000 kg/m3) times its approximate volume. m = Ax(1000) kg