中小学教育资源及组卷应用平台
人教版数学六年级上册
计算专项(一)
归纳总结:
分数乘整数,分母分不用变。分子与整数,乘积作分子。计算想简便,约分要在先。结果要想准,分数化最简。
分数乘分数:用分子相乘的积作分子,用分母相乘的积作分母。用字母表示为:
× = (a≠0,c≠0)
小数乘分数:①把小数化成分数计算;②如果所乘的分数能化成有限小数,也可以把分数化成小数计算;③小数和分母能约分的,先约分再计算比较简便。
(背)常见分数小数互化: = 0.5 ; = 0.25 ; = 0.75; = 0.2; = 0.4; = 0.6;
= 0.8 ; = 0.125; = 0.375 ; = 0.625 ; = 0.875。
分数除法:一个数(可以是整数、分数、也可以是小数)除以分数,等于乘这个分数的倒数;一个数(0除外)除以一个不等于0的数,等于一个数乘这个数的倒数。
①分数除以整数(0除外)等于分数乘这个整数的倒数。用字母表示: ÷ n = × (a≠0,n≠0);
②整数除以分数: 用字母表示为 a÷ = a× (m≠0,n≠0);
③分数除以分数:用字母表示为 ÷ = × (a≠0,m≠0,n≠0)
分数混合运算顺序:没有括号的,先算乘除法,再算加减法;有括号的,先算括号里的,再算括号外面的。
整数乘法运算定律推广到分数乘法:乘法交换律:a×b = b×a;
乘法结合律:(a×b )×c = a×(b ×c); 乘法分配律:(a + b)×c = a×c + b×c
一、计算
直接写得数
12× = 2 - = 0.25 + = 1÷ = 2.1× = 0÷ = ÷ 5 = - = 3.5÷ = × × = + - + = 1.4× = ×30 +6= 1÷2% = ÷ × ÷ = 24% × 5 = 0.7 × = 4× × 0.25 =
计算下面各题,能简算的要简算
( + )×20 75× + 26×75% - + + +
÷ × ( - )×18 × + ×
13.7× + 11.3÷ × + ×0.75 (2- )+ ÷ 0.5
÷ [(1.2+ )×2] + × ÷ ( + 2.5 × )×
101× - 87× × 11 -
× ×24×25 × + × 36×( - + )
÷ + × 7.2 20÷ [8×( - )] ÷ [( - 1.1)× ]
解方程
- = + = 4.6 0.375 + =1
2.4 - = 7 6 ÷ = 15 - = 0.22
列综合算式或方程解答下面各题。
与 的差除以 的商是多少? (2)一个数的 比20多36,求这个数。
一个数的40%是24,这个数是多少? (4)50的 比它的20%多多少?
参考答案
计算
直接写得数:10, , , ,0.7,0, , ,5, ,1, ,20,50, ,1.2,0.5, 。
计算下面各题,能简算的要简算
( + )×20 75× + 26×75% - + + +
= ×20+ ×20 = ×(75+26-1) =( + )+( + )
=15+8 = ×100 =1+3
=23 =75 = 4
÷ × ( - )×18 × + ×
= × ( ×) = ×18 - ×18 = ×( + )
= × = 10-3 = ×1
= = 7 =
13.7× + 11.3÷ × + ×0.75 (2- )+ ÷ 0.5
=(13.7+11.3)× = ×( + ) = + ×2
=25× = ×1 = +
=30 = =
÷ [(1.2+ )×2] + × ÷ ( + 2.5 × )×
= ÷ [( + )×2] = + × × = ( + 2 )×
= ÷[ ×2] = + × = ×
= ÷3 = =
= =
101× - 87× × 11 -
=(101-1)× =(86 +1) × =(11 -1)×
= 100× = 86× +1× = 10 ×
=20 =3 + = 9
= 3
× ×24×25 × + × 36×( - + )
= (×24)× (×25) = ( + )× = 36× - 36× + 36×
=9× =2× =12-10+21
=237 = =23
÷ + × 7.2 20÷ [8×( - )] ÷ [( - 1.1)× ]
= ×3+ × 7.2 =20÷ [8×( - )] = ÷ [(1.5 - 1.1)× ]
= + 2.2 = 20÷ [8×] = ÷ [(0.4× ]
= 1.25+2.2 =20÷ = ÷0.3
=3.45 =35 = ×
= 6
3.解方程
- = + = 4.6 0.375 + =1
解: = + 解: = 4.6 解: + = 1
= = 4.6× = 1-
= × = 4 =
= = ×4
=
2.4 - = 7 6 ÷ = 15 - = 0.22
解: 1.4 = 7 解: 6 =15× 解: = 0.22
= 7÷1.4 6 = 9 =0.22×
= 5 = = 0.4
4.列综合算式或方程解答下面各题。
(1)( - )÷ = (2)(36+20)÷ =105
(3)解:设这个数是 (4)50×( - 20%)= 30
40%=24
= 24÷0.4
= 60
21世纪教育网 www.21cnjy.com 精品试卷·第 2 页 (共 2 页)
21世纪教育网(www.21cnjy.com)