0.23+0.27+0.31+0.35+…+0.63+0.67
=（0.23+0.67）+（0.27+0.63）+（0.31+0.59）+（0.35+0.55）+（0.39+0.51）+（0.43+0.47）
=0.9+0.9+0.9+0.9+0.9+0.9
=0.9×6
=5.4