Question

口算： 1 2 ÷0.25=	6 5 × 5 8 =	21× 12 7 =
1÷5× 1 5 =	4 3 5 - 3 11 - 8 11 =	100×2.5%=
1÷5- 1 5 + 3 4 =	5 8 -0×8=	4 5 × 3 4 =
8 9 ×27=	1 3 ÷4=	5-2 3 4 + 1 4 =
1 2 + 1 4 + 1 8 =	11 12 - 5 6 + 1 12 =

Answer 1

分析：分數(shù)乘整數(shù)，用分數(shù)的分子和整數(shù)相乘的積做分子，分母不變；分數(shù)乘分數(shù)，用分子相乘的積做分子，分母相乘的積做分母，能約分的要約分；分數(shù)除以一個數(shù)，等于乘這個數(shù)的倒數(shù)；以及分數(shù)四則運算的法則，即可求解．

解答：解：

1 2 ÷0.25=2	6 5 × 5 8 = 3 4	21× 12 7 =36
1÷5× 1 5 = 1 25	4 3 5 - 3 11 - 8 11 =3 3 5	100×2.5%=2.5
1÷5- 1 5 + 3 4 = 3 4	5 8 -0×8= 5 8	4 5 × 3 4 = 3 5
8 9 ×27=24	1 3 ÷4= 1 12	5-2 3 4 + 1 4 = 5 2
1 2 + 1 4 + 1 8 = 7 8	11 12 - 5 6 + 1 12 = 1 6

點評：此題主要考查分數(shù)乘法、除法和分數(shù)四則運算法則的靈活應用；同時也考查了學生的口算能力．