TÍNH NHANH
a)15x14-1
13x15+14
b)9x(262626+88888)
272727 99999
c)1+2+3+4+5+6+7+8+9
10
d)4343+4343+4343+4343
7171 7171 7171 7171
bài phân số
a, \(\dfrac{15\times14-1}{13\times15+14}\)
= \(\dfrac{15\times\left(13+1\right)-1}{13\times15+14}\)
= \(\dfrac{13\times15+15-1}{13\times15+14}\)
= \(\dfrac{13\times15+14}{13\times15+14}\)
= 1
c, \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(9+1\right)\times\left\{\left(9-1\right):1+1\right\}:2}{10}\)
= \(\dfrac{10\times9:2}{10}\)
= \(\dfrac{9}{2}\)
Tính:
S = \(\left(\frac{17}{71}+\frac{1717}{7171}+\frac{171717}{717171}\right):\frac{17171717}{71717171}\)
\(S=\left(\frac{17}{71}+\frac{17.101}{71.101}+\frac{17.10101}{71.10101}\right):\frac{17.1010101}{71.1010101}\)
\(S=\left(\frac{17}{71}+\frac{17}{71}+\frac{17}{71}\right):\frac{17}{71}\)
\(S=3.\frac{17}{71}:\frac{17}{71}=3\)
\(S=\left(\frac{17}{71}+\frac{17.101}{71.101}+\frac{17.10101}{71.10101}\right):\frac{17.1010101}{71.1010101}\)
\(S=\left(\frac{17}{71}+\frac{17}{71}+\frac{17}{71}\right):\frac{17}{71}\)
\(S=3.\frac{17}{71}:\frac{17}{71}\)
\(\Rightarrow S=3\)
Rất vui vì giúp đc bạn <3
Chứng tỏ rằng :
\(\frac{7171}{3939}=\frac{717171}{393939}\).
Ai làm đúng thì tick.
Cách 1 : Ta "rút gọn" hai phân số trên :
\(\frac{7171}{3939}=\frac{717171}{393939}=\frac{71}{39}\).
Cách 2 : Ta "nhân chéo" hai phân số đó :
\(\frac{7171}{3939}=\frac{717171}{393939}\Rightarrow7171\times393939=717171\times3939(=2.824.936.569)\).
\(\frac{7171}{3939}=\frac{71\times101}{39\times101}=\frac{71}{39}\)
\(\frac{717171}{393939}=\frac{71\times10101}{39\times10101}=\frac{71}{39}\)
Ta có:\(\frac{71}{39}=\frac{71}{39}\)
\(\rightarrow\frac{7171}{3939}=\frac{717171}{393939}\)
Giúp tôi giải toán:
Tính bằng cách thuận tiện nhất
15 x \(\frac{2121}{4343}\)+ 15 x \(\frac{222222}{434343}\)
\(15x\frac{2121}{4343}+15x\frac{222222}{434343}\)
\(=15x\frac{21}{43}+15x\frac{22}{43}\)
\(=15x\left(\frac{21}{43}+\frac{22}{43}\right)\)
\(=15x1\)
\(=15\)
= 15 x 21/43 + 15x 22/43
= 15 x (21/43 + 22/43)
= 15 x 1 =15
\(15\cdot\frac{2121}{4343}+15\cdot\frac{222222}{434343}\) =\(15\cdot\left(\frac{2121}{4343}+\frac{222222}{434343}\right)\) =\(15\cdot\left(\frac{21}{43}+\frac{22}{43}\right)\) =\(15\cdot\frac{43}{43}\) =\(15\cdot1=15\) tish cho mk nhé
\(\frac{244}{537}\)+\(\frac{132}{354}\)+\(\frac{4343}{4342}\)+\(\frac{4324}{4545}\) * 0 = ?
Tính :
A = \(\frac{3737\times43-4343\times37}{2+4+6+........+2018}\)
A = \(\frac{3737x43-4343x37}{2+4+6+...+2018}\)
A = \(\frac{37x101x43-43x101x37}{2+4+6+..+2018}\)
A = \(\frac{0}{2+4+6+..+2018}\) = 0
bài 1 Tính
a) C =\(\frac{101+100+99+98+....+3+2+1}{101-100+99-98+....+3-2+1}\)
b) D = \(\frac{3737\cdot43-4343\cdot37}{2+4+6+....+100}\)
C = \(\frac{101+100+99+98+...+3+2+1}{101-100+99-98+...+3-2+1}\)
\(C=\frac{\left(101+1\right).101:2}{1+1+...+1+1}\)
\(C=\frac{5151}{51}\)
\(C=101\)
b) \(D=\frac{3737.43-4343.37}{2+4+6+...+100}\)
\(D=\frac{37.101.43-43.101.37}{2+4+6+...+100}\)
\(D=\frac{0}{2+4+6+...+100}\)
\(D=0\)
a) \(C=\frac{101+100+99+98+...+3+2+1}{101-100+99-98...+3-2+1}\)
\(=\frac{\left(101+1\right).\left[\left(101-1\right):1+1\right]:2}{\left(101-100\right)+\left(99-98\right)+\left(3-2\right)+1}\)
\(=\frac{102.101:2}{1+1+...+1}\)
\(=\frac{51.101}{51}\)
\(=101.\)
Tính nhanh :
\(\frac{7}{4}x\left(\frac{33}{12}+\frac{33}{20}+\frac{33}{30}+\frac{33}{42}\right)\)
\(\frac{7}{4}\)x(\(\frac{33}{12}\)+\(\frac{33}{20}\)+\(\frac{33}{30}\)+\(\frac{33}{42}\))
=\(\frac{7}{4}\)x\(\frac{44}{7}\)
=\(\frac{308}{28}\)=11
Tính:
a) \(A=\frac{101+100+99+98+..+3+2+1}{101-100+99-98+..+3-2+1}\)
b)\(B=\frac{3737\cdot43-4343\cdot37}{2+4+6+...+100}\)
Giải chi tiết nha các bn
