1/7x1/2:1/7= 1/7x1/2x....=....?
1/7x1/7-3/7x1/7-3/8+1/3 tính kiểu gì cũng được
1/5x4/7-3/7x1/5-1/5
1/5x (4/7- 3/7- 1)=1/5x -6/7= -6/35
1/5x4/7+3/7x1/5-1/5
\(\dfrac{1}{5}\times\dfrac{4}{7}+\dfrac{3}{7}\times\dfrac{1}{5}-\dfrac{1}{5}\)
\(=\dfrac{4}{35}+\dfrac{3}{35}-\dfrac{1}{5}\)
\(=\dfrac{7}{35}-\dfrac{1}{5}\)
\(=\dfrac{1}{5}-\dfrac{1}{5}\)
\(=0\)
Tính nhanh
5/6x1/7-1/7x1/6
8/15:4/5x3/2
5/6 x 1/7 - 1/7 x 1/6
= 1/7 x (5/6 - 1/6)
= 1/7 x 2/3
= 2/21
8/15 : 4/5 x 3/2
= 2/3 x 3/2
= 1
a: =1/7(5/6-1/6)=1/7x2/3=2/21
b: =8/15x5/4x3/2=1
`5/6xx1/7-1/7xx1/6`
`= 1/7 xx (5/6-1/6)`
`= 1/7 xx 2/3`
`= 2/21`
`8/15: 4/5 xx3/2`
`= 2/3 xx 3/2`
`= 1`
6/7x1/3
6/7- 1/3
tính nhanh 3/7x1/5+2/3x3/7-3/7x1/8 giúp mình với mình đang cần gấp
\(=\dfrac{3}{7}\times\left(\dfrac{1}{5}+\dfrac{2}{3}-\dfrac{1}{8}\right)\\ =\dfrac{3}{7}\times\left(\dfrac{24}{5\times24}+\dfrac{2\times40}{3\times40}-\dfrac{15}{8\times15}\right)\\ =\dfrac{3}{7}\times\left(\dfrac{24+80-15}{120}\right)\\ =\dfrac{3}{7}\times\dfrac{89}{120}\\ =\dfrac{89}{280}\)
\(\dfrac{3}{7}\times\dfrac{1}{5}+\dfrac{2}{3}\times\dfrac{3}{7}-\dfrac{3}{7}\times\dfrac{1}{8}\)
\(=\dfrac{3}{7}\times\left(\dfrac{1}{5}+\dfrac{3}{7}-\dfrac{1}{8}\right)\)
\(=\dfrac{3}{7}\times\dfrac{56+120-35}{280}\)
\(=\dfrac{3}{7}\times\dfrac{141}{280}\)
\(=\dfrac{423}{1960}\)
B=(1/7+1/23-1/1009):(1/7+1/23-1/1009+1/7x1/23x1/1009)+1:(30x1009-160)
tính : A=(1/7+1/23-1/1009):(1/23+1/7-1/1009+1/7x1/23x1/1009)+1:(30x1009-160)
suy ra A=1/23+1/7-1/1009.23.7.1009 phần 1/23+1/7-1/1009+1/7.1/3/1/1009 .23.7.1009+1/30.1009-160
suy ra A=7.1009+23.1009-23.7/7.1009+23.1009-23.7+1 +1/7.1009+23.1009-23.7+1=7/1009+23.1009- 23.7+1/7.1009+23.1009-23.7+1=1
1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7+1/7x1/8+1/8x1/9
1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7+1/7x1/8+1/8x1/9
=7/18