内容正文:
第五单元计算专项:含百分数的运算及简算
知识点梳理
1. 百分数加减乘除运算:先把百分数化成小数或者分数,再进行计算。
2. 运算顺序:先乘除,后加减;有括号先算括号里面;同级运算从左往右。
3. 简便运算:可以运用乘法交换律、结合律、分配律进行简算。
乘法分配律:
4. 常用转化:,,,
专项练习
考点1:百分数与小数、分数普通四则计算(无简算)
(1)1 + 25%
(2)1 - 40%
(3)80% × 5
(4)3 ÷ 60%
(5)0.5 + 35%
(6) - 20%
(7)120% × 0.2
(8) ÷ 75%
(9)4 - 12.5%
(10)0.8 × 50%
考点2:百分数混合运算(先乘除后加减)
(1)20 + 80% × 10
(2)15 - 30% × 20
(3)40% × 5 +
(4)6 ÷ 20% - 15
(5)0.7 + 30% ÷ 0.3
(6)1 - × 40%
(7)25 × 40% + 1.6
(8)72 ÷ 90% - 50
(9) + 60% × 2
(10)10 - 4.8 ÷ 80%
考点3:带括号的百分数运算
(1)(1 + 50%) × 4
(2)(1 - 25%) ÷ 0.75
(3)(20 + 10) × 30%
(4)(0.8 - 40%) ÷ 0.2
(5)( + 20%) × 10
(6)(12 - 4) × 75%
(7)(1 + 12.5%) × 8
(8)(3.6 + 2.4) ÷ 60%
(9)( - 50%) × 20
(10)(100 - 40) × 15%
考点4:乘法分配律简算(百分数)
(1)36×25% + 64×25%
(2)72×60% + 28×60%
(3)120×(50% + 25%)
(4)4.8×75% - 2.8×75%
(5)×40% + ×40%
(6)8×12.5% + 8×87.5%
(7)150×(1 - 30%)
(8)0.6×120% - 0.6×20%
(9)24×75% + 24×25%
(10)50×18% + 50×82%
考点5:百分数连乘、连除简便运算
(1)2.5 × 32 × 25%
(2)12.5% × 0.7 × 8
(3)4 × 78% × 25
(4)48 ÷ 25% ÷ 4
(5)0.8 × 12.5% × 10
(6)360 ÷ (9 × 20%)
(7) × 5.6 × 4
(8)5.4 ÷ 18% ÷ 3
(9)8 × 72% × 125
(10)100 ÷ 12.5% ÷ 8
对应应用题
1. 一个数是80,加上它的25%,结果是多少?
2. 一根绳子长40米,减去它的40%,还剩多少米?
3. 一件商品原价120元,涨价10%,涨价后价格多少元?
4. 甲数是60,乙数是甲数的75%,甲乙两数一共多少?
5. 一堆煤50吨,先用去30%,再用去5吨,还剩多少吨?
6. 果园有果树200棵,其中45%是苹果树,其余是梨树,梨树多少棵?
7. 一本书共160页,已经看了60%,还剩多少页没有看?
8. 某工厂上月产量150件,本月比上月增加20%,本月产量多少件?
9. 一块长方形地,长30米,宽是长的50%,这块地面积是多少平方米?
10. 有24千克盐水,含盐率12.5%,盐有多少千克?
专项训练
第 1 页 共 6 页
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参考答案
考点1:百分数与小数、分数普通四则计算(无简算)
(1)1 + 25% = 1 + 0.25 = 1.25
(2)1 - 40% = 1 - 0.4 = 0.6
(3)80% × 5 = 0.8 × 5 = 4
(4)3 ÷ 60% = 3 ÷ 0.6 = 5
(5)0.5 + 35% = 0.5 + 0.35 = 0.85
(6) - 20% = 0.5 - 0.2 = 0.3
(7)120% × 0.2 = 1.2 × 0.2 = 0.24
(8) ÷ 75% = 0.75 ÷ 0.75 = 1
(9)4 - 12.5% = 4 - 0.125 = 3.875
(10)0.8 × 50% = 0.8 × 0.5 = 0.4
考点2:百分数混合运算(先乘除后加减)
(1)20 + 80% × 10 = 20 + 0.8×10 = 20 + 8 = 28
(2)15 - 30% × 20 = 15 - 0.3×20 = 15 - 6 = 9
(3)40% × 5 + = 0.4×5 + 0.5 = 2 + 0.5 = 2.5
(4)6 ÷ 20% - 15 = 6 ÷ 0.2 - 15 = 30 - 15 = 15
(5)0.7 + 30% ÷ 0.3 = 0.7 + 0.3÷0.3 = 0.7 + 1 = 1.7
(6)1 - × 40% = 1 - 0.25×0.4 = 1 - 0.1 = 0.9
(7)25 × 40% + 1.6 = 25×0.4 + 1.6 = 10 + 1.6 = 11.6
(8)72 ÷ 90% - 50 = 72 ÷ 0.9 - 50 = 80 - 50 = 30
(9) + 60% × 2 = 0.6 + 0.6×2 = 0.6 + 1.2 = 1.8
(10)10 - 4.8 ÷ 80% = 10 - 4.8÷0.8 = 10 - 6 = 4
考点3:带括号的百分数运算
(1)(1 + 50%) × 4 = (1 + 0.5) × 4 = 1.5 × 4 = 6
(2)(1 - 25%) ÷ 0.75 = (1 - 0.25) ÷ 0.75 = 0.75 ÷ 0.75 = 1
(3)(20 + 10) × 30% = 30 × 0.3 = 9
(4)(0.8 - 40%) ÷ 0.2 = (0.8 - 0.4) ÷ 0.2 = 0.4 ÷ 0.2 = 2
(5)( + 20%) × 10 = (0.5 + 0.2) × 10 = 0.7 × 10 = 7
(6)(12 - 4) × 75% = 8 × 0.75 = 6
(7)(1 + 12.5%) × 8 = (1 + 0.125) × 8 = 1.125 × 8 = 9
(8)(3.6 + 2.4) ÷ 60% = 6 ÷ 0.6 = 10
(9)( - 50%) × 20 = (0.75 - 0.5) × 20 = 0.25 × 20 = 5
(10)(100 - 40) × 15% = 60 × 0.15 = 9
考点4:乘法分配律简算(百分数)
(1)36×25% + 64×25% = (36+64) × 0.25 = 100 × 0.25 = 25
(2)72×60% + 28×60% = (72+28) × 0.6 = 100 × 0.6 = 60
(3)120×(50% + 25%) = 120×0.5 + 120×0.25 = 60 + 30 = 90
(4)4.8×75% - 2.8×75% = (4.8-2.8) × 0.75 = 2 × 0.75 = 1.5
(5)×40% + ×40% = ( + ) × 0.4 = 1 × 0.4 = 0.4
(6)8×12.5% + 8×87.5% = 8 × (0.125+0.875) = 8 × 1 = 8
(7)150×(1 - 30%) = 150×1 - 150×0.3 = 150 - 45 = 105
(8)0.6×120% - 0.6×20% = 0.6 × (1.2-0.2) = 0.6 × 1 = 0.6
(9)24×75% + 24×25% = 24 × (0.75+0.25) = 24 × 1 = 24
(10)50×18% + 50×82% = 50 × (0.18+0.82) = 50 × 1 = 50
考点5:百分数连乘、连除简便运算
(1)2.5×32×25% = 2.5×8×4×0.25 = (2.5×8) × (4×0.25) = 20 × 1 = 20
(2)12.5%×0.7×8 = 0.125×8×0.7 = 1 × 0.7 = 0.7
(3)4×78%×25 = 4×25×0.78 = 100 × 0.78 = 78
(4)48÷25%÷4 = 48 ÷ (0.25×4) = 48 ÷ 1 = 48
(5)0.8×12.5%×10 = 0.8×0.125×10 = 0.1 × 10 = 1
(6)360÷(9×20%) = 360÷9÷0.2 = 40 ÷ 0.2 = 200
(7)×5.6×4 = ×4×5.6 = 1 × 5.6 = 5.6
(8)5.4÷18%÷3 = 5.4÷0.18÷3 = 30 ÷ 3 = 10
(9)8×72%×125 = 8×125×0.72 = 1000 × 0.72 = 720
(10)100÷12.5%÷8 = 100 ÷ (0.125×8) = 100 ÷ 1 = 100
应用题参考答案与计算过程
1. 80 + 80×25% = 80 + 20 = 100
答:结果是100。
2. 40 × (1 - 40%) = 40 × 0.6 = 24(米)
答:还剩24米。
3. 120 × (1 + 10%) = 120 × 1.1 = 132(元)
答:涨价后价格132元。
4. 60 + 60×75% = 60 + 45 = 105
答:甲乙两数一共105。
5. 50 - 50×30% - 5 = 50 - 15 - 5 = 30(吨)
答:还剩30吨。
6. 200 × (1 - 45%) = 200 × 0.55 = 110(棵)
答:梨树110棵。
7. 160 × (1 - 60%) = 160 × 0.4 = 64(页)
答:还剩64页没有看。
8. 150 × (1 + 20%) = 150 × 1.2 = 180(件)
答:本月产量180件。
9. 宽:30×50% = 15(米),面积:30×15 = 450(平方米)
答:面积是450平方米。
10. 24 × 12.5% = 24 × 0.125 = 3(千克)
答:盐有3千克。
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