(1) 1 3 ×12.3×7=4.1×7=28.7(cm3);答:图①中圆锥的体积是12.56cm3.(2) 1 3 ×3.14×(6÷2)2×8= 1 3 ×3.14×4×9×8=3.14×4×3×8=301.44(dm3);答:图②中圆锥的体积是301.44dm3.(3) 1 3 ×3.14×22×1.5= 1 3 ×3.14×4×1.5=3.14×4×0.5=6.28(m3);答:图③中圆锥的体积是6.28m3.