Tính bằng 2 cách :
Cách 1 : ( 2/3-1/4) * 1/2 = .......................................
cách 2 : ( 2/3-1/4) * 1/2 = ........................................
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a) Cách 1 : (3/4 + 1/2) x 5/7
= 5/4 x 5/7
= 25/28
Cách 2 : (3/4 + 1/2) x 5/7
= 3/4 x 5/7 + 1/2 x 5/7
= 15/28 + 5/14
= 25/28
b) Cách 1 : 5/7 x 13/21 + 2/7 x 13/21
= 65/147 + 26/147
= 13/21
Cách 2 : 5/7 x 13/21 + 2/7 x 13/21
= (5/7 + 2/7) x 13/21
= 1 x 13/21
= 13/21
câu c tự làm
a) Cách 1
\(\frac{3}{4}\)x \(\frac{1}{2}\)x \(2\)
= \(\frac{3}{8}\)x \(2\)
= \(\frac{3}{4}\)
Cách 2
\(\frac{3}{4}\)x \(\frac{1}{2}\)x \(2\)
= \(\frac{3}{4}\)x \(\left(\frac{1}{2}x2\right)\)
= \(\frac{3}{4}\)x 1
= \(\frac{3}{4}\)
`(1/3 + 1/5) xx 1/4`
`= ( 5/15 + 3/15) xx 1/4`
`= 8/15 xx 1/4`
`= 8/60`
`= 2/15`
__
`(1/3 + 1/5) xx 1/4`
`= 1/3 xx 1/4 + 1/5 xx 1/4`
`= 1/12 +1/20`
`=2/15`
\(C_1:\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\times\dfrac{1}{4}=\dfrac{1}{4}\times\dfrac{1}{3}+\dfrac{1}{4}\times\dfrac{1}{5}=\dfrac{1}{12}+\dfrac{1}{20}=\dfrac{2}{15}\)
\(C_2:\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\times\dfrac{1}{4}=\dfrac{8}{15}\times\dfrac{1}{4}=\dfrac{8\times1}{15\times4}=\dfrac{8}{60}=\dfrac{2}{15}\)
1/2 + 1/3 + 1/4 + 1/5 + 4/5 + 3/4 + 2/3 + 1/2
= (1/2 + 1/2) + (1/3 + 2/3) + (1/4 + 3/4) + (1/5 + 4/5)
= 1 + 1 + 1 + 1
= 4
\(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{3}{4}+\dfrac{2}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{1}{2}+\dfrac{1}{2}\right)+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{4}+\dfrac{3}{4}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)\)
=1+1+1+1
=4
1/2 + 1/3 + 1/4 + 1/5 + 4/5 + 3/4 + 2/3 + 1/2
= (1/2 + 1/2) + (1/3 + 2/3) + (1/4 + 3/4) + (1/5 + 4/5)
= 1 + 1 + 1 + 1
= 4
Cách 1
\(\left(\frac{2}{3}-\frac{1}{4}\right)\cdot\frac{1}{2}=\left(\frac{8}{12}-\frac{3}{12}\right)\cdot\frac{1}{2}=\frac{5}{12}\cdot\frac{1}{2}=\frac{5}{24}\)
Cách 2\(\left(\frac{2}{3}-\frac{1}{4}\right)\cdot\frac{1}{2}=\frac{2}{3}\cdot\frac{1}{2}-\frac{1}{4}\cdot\frac{1}{2}=\frac{1}{3}-\frac{1}{8}=\frac{8}{24}-\frac{3}{24}=\frac{5}{24}\)
Cách 1 : (2/3 - 1/4) x 1/2
= 5/12 x 1/2
= 5/24
Cách 2 : (2/3 - 1/4) x 1/2
= 2/3 x 1/2 - 1/4 x 1/2
= 1/3 - 1/8
= 5/24
kb vs tớ nha