一个棱长总和是84cm的正方体,它的表面积是 ,体积是 .
60%= :15== ÷20= (写小数)
:10=18: =50%=6: = ÷60.
35: =20÷16== %= (填小数)
:3=10: ==1.5: .
30:42==45÷ ≈ %.