\(\dfrac{3}{4}\)+\(\dfrac{2}{4}\)+\(\dfrac{4}{4}\)+\(\dfrac{3}{4}\)=
CHỦ ĐỀ:tính bằng cách thuận tiện nhất
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\(\dfrac{2}{3}\times\dfrac{3}{4}\times\dfrac{4}{5}\) \(=\dfrac{2\times3\times4}{3\times4\times5}\) \(=\) \(\dfrac{2}{5}\)
\(\dfrac{2}{3}x\dfrac{3}{4}x\dfrac{4}{5}=\dfrac{2}{5}\)
\(\dfrac{4}{7}x\left(\dfrac{2}{5}+\dfrac{3}{5}\right)=\dfrac{4}{7}x1=\dfrac{4}{7}\)
\(B=\dfrac{1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}}{4+\dfrac{4}{7}+\dfrac{4}{7^2}-\dfrac{4}{7^3}}\cdot\dfrac{858585}{313131}\cdot\left(-1\dfrac{14}{17}\right)\)
\(=\dfrac{1}{4}\cdot\dfrac{85}{31}\cdot\dfrac{-31}{17}\)
\(=\dfrac{-5}{4}\)
\(=\dfrac{16+25}{20}\cdot\dfrac{3}{4}=\dfrac{41}{20}\cdot\dfrac{3}{4}=\dfrac{123}{80}\)
`3/4+2/5+3/12`
`=3/4+3/12+2/5`
`=9/12+3/12+2/5`
`=12/12+2/5`
`=1+2/5`
`=7/5`
\(\dfrac{7}{6}\times\dfrac{3}{4}+\dfrac{3}{4}\times\dfrac{5}{6}-\dfrac{3}{4}\\ =\left(\dfrac{7}{6}+\dfrac{5}{6}-1\right)\times\dfrac{3}{4}\\ =1\times\dfrac{3}{4}=\dfrac{3}{4}\\ \dfrac{6\times7\times15\times8}{4\times21\times10\times3}\\ =\dfrac{2\times3\times7\times5\times3\times4\times2}{4\times7\times3\times5\times2\times3}\\ =2\)
1.
=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1
= 2/5 x (12/3 + 15/3 + 1)
=2/5 x 1
=2/5
2.a=1;2
a: =20/90+15/90+54/90=89/90
b: =(9/13+4/13)+2/3=1+2/3=5/3
\(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{4}{7}+\dfrac{5}{7}+\dfrac{6}{7}\)
\(=\dfrac{1+2+3+4+5+6}{7}=3\)
\(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{4}{7}+\dfrac{5}{7}+\dfrac{6}{7}\)
\(=\left(\dfrac{1}{7}+\dfrac{6}{7}\right)+\left(\dfrac{2}{7}+\dfrac{5}{7}\right)+\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\)
\(=1+1+1\)
\(=3\)
\(=\dfrac{12}{4}=3\)