Question

口算．

21%+5%	8 9 ÷4	8π	3 8 + 3 4	125×8
4 7 × 3 8	1 3 + 1 4	2 3 - 1 2	3 4 ÷ 6 7	8÷64
7 10 × 5 14	7π	2 3 + 5 6	2 3 × 5 6	13÷26
6 7 - 3 14	67%-24%	99×5	9 10 × 5 6	2 3 × 9 10
6 7 ÷ 6 5	100÷25	1 6 × 3 4	7 10 × 5 21	5 8 × 4 15
3 4 ÷ 6 7	667+34	4 7 ÷ 9 14	11 12 ÷ 11 14	1263-163
2 5 ÷ 5 6	9 10 × 5 6	4 7 ÷ 7 8	12 2 ÷ 3 4	98%-55%
11 15 ÷ 22 45	4 7 × 7 8	15.7÷3.14	6 7 - 3 14	7 9 × 5 21
7 12 ÷ 7 8	9 11 ÷ 3 22	6 7 + 3 14	4 5 ÷ 3 4	5 9 × 2 15
5 9 ÷ 2 15	2 3 × 4 9	6.28÷π	0× 7 8	21÷5
8 9 × 4 5	14 15 ÷ 7 10	39× 4 13	3π	66×10
0÷875	1- 1 2 - 1 3	（ 1 3 - 1 4 ）×12	5 7 × 1 6 + 5 7 × 5 6	3- 2 9 - 7 9

Answer 1

分析：根據(jù)所給的題目的特點，可分為以下幾類：一類是分數(shù)加、減法，如果是同分母的分數(shù)相加減，分母不變，分子相加減，如果是異分母的分數(shù)相加減，先化成同分母的分數(shù)，再計算；二類是分數(shù)乘法，分數(shù)乘整數(shù)時，用分數(shù)的分子和整數(shù)相乘的積做分子，分母不變，（能約分要在計算中先約分 ）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，能約分的要約成最簡分數(shù)（在計算中約分）；三類是分數(shù)除法，即除以一個數(shù)等于乘這個數(shù)的倒數(shù)．

解答：解：

21%+5%=26%	8 9 ÷4= 2 9	8π=25.12	3 8 + 3 4 = 9 8	125×8=1000
4 7 × 3 8 = 3 14	1 3 + 1 4 = 7 12	2 3 - 1 2 = 1 6	3 4 ÷ 6 7 = 7 8	8÷64= 1 8
7 10 × 5 14 = 1 4	7π=21.98	2 3 + 5 6 = 3 2	2 3 × 5 6 = 5 9	13÷26= 1 2
6 7 - 3 14 = 9 14	67%-24%=43%	99×5=495	9 10 × 5 6 = 3 4	2 3 × 9 10 = 3 5
6 7 ÷ 6 5 = 5 7	100÷25=4	1 6 × 3 4 = 1 8	7 10 × 5 21 = 1 6	5 8 × 4 15 = 1 6
3 4 ÷ 6 7 = 7 8	667+34=700	4 7 ÷ 9 14 = 8 9	11 12 ÷ 11 14 = 7 6	1263-163=1100
2 5 ÷ 5 6 = 12 25	9 10 × 5 6 = 3 4	4 7 ÷ 7 8 = 32 49	12 2 ÷ 3 4 =8	98%-55%=43%
11 15 ÷ 22 45 = 3 2	4 7 × 7 8 = 1 2	15.7÷3.14=5	6 7 - 3 14 = 9 14	7 9 × 5 21 = 5 27
7 12 ÷ 7 8 = 2 3	9 11 ÷ 3 22 =6	6 7 + 3 14 = 15 14	4 5 ÷ 3 4 = 16 15	5 9 × 2 15 = 2 27
5 9 ÷ 2 15 = 25 6	2 3 × 4 9 = 8 27	6.28÷π=2	0× 7 8 =0	21÷5= 21 5
8 9 × 4 5 = 32 45	14 15 ÷ 7 10 = 4 3	39× 4 13 =12	3π=3×3.14=9.42	66×10=660
0÷875=0	1- 1 2 - 1 3 = 1 6	（ 1 3 - 1 4 ）×12=1	5 7 × 1 6 + 5 7 × 5 6 = 5 7	3- 2 9 - 7 9 =2

點評：解答此題的關(guān)鍵是，能夠熟練掌握，四則運算的方法，口算時，能簡算的一定盡量用一些簡便的方法計算，以提高口算速度．