\(\dfrac{3}{4}\)+\(\dfrac{2}{4}\)+\(\dfrac{4}{4}\)+\(\dfrac{3}{4}\)=
CHỦ ĐỀ:tính bằng cách thuận tiện nhất
Tính bằng cách thuận tiện nhất
\(\dfrac{2}{3}\times\dfrac{3}{4}\times\dfrac{4}{5}\)
\(\dfrac{2}{3}\times\dfrac{3}{4}\times\dfrac{4}{5}\) \(=\dfrac{2\times3\times4}{3\times4\times5}\) \(=\) \(\dfrac{2}{5}\)
\(\dfrac{2}{3}x\dfrac{3}{4}x\dfrac{4}{5}=\dfrac{2}{5}\)
\(\dfrac{2}{3}\)x\(\dfrac{3}{5}\)=\(\dfrac{2}{5}\)
Tính bằng cách thuận tiện nhất:
\(\dfrac{2}{5}\) *\(\dfrac{4}{7}\)+\(\dfrac{3}{5}\)*\(\dfrac{4}{7}\)
\(\dfrac{4}{7}x\left(\dfrac{2}{5}+\dfrac{3}{5}\right)=\dfrac{4}{7}x1=\dfrac{4}{7}\)
2/5 x 4/7 + 3/5 x 4/7
= (2/5 + 3/5 ) x 4/7
= 1 x 4/7
= 4/7
2/5 *4/7+3/5*4/7
=( 2/5 + 3/5 ) *4/7
= 1 * 4/7
= 4/7
Tính bằng cách thuận tiện nhất
B=\(\dfrac{1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}}{4+\dfrac{4}{7}+\dfrac{4}{7^2}-\dfrac{4}{7^3}}x\dfrac{858585}{313131}x\left(-1\dfrac{14}{17}\right)\)
\(B=\dfrac{1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}}{4+\dfrac{4}{7}+\dfrac{4}{7^2}-\dfrac{4}{7^3}}\cdot\dfrac{858585}{313131}\cdot\left(-1\dfrac{14}{17}\right)\)
\(=\dfrac{1}{4}\cdot\dfrac{85}{31}\cdot\dfrac{-31}{17}\)
\(=\dfrac{-5}{4}\)
Ta có: \(B=\dfrac{1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}}{4+\dfrac{4}{7}+\dfrac{4}{7^2}-\dfrac{4}{7^3}}.\dfrac{858585}{313131}.\left(-1\dfrac{14}{17}\right)\)
\(=\dfrac{1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}}{4\left(1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}\right)}.\dfrac{85.10101}{32.10101}.\dfrac{-31}{17}=\dfrac{1}{4}.\dfrac{85}{31}.\dfrac{-31}{17}=-\dfrac{5}{4}\)
tính bằng cách thuận tiện nhất
\(\left(\dfrac{4}{5}+\dfrac{5}{4}\right)\)x\(\dfrac{3}{4}\)
\(=\dfrac{16+25}{20}\cdot\dfrac{3}{4}=\dfrac{41}{20}\cdot\dfrac{3}{4}=\dfrac{123}{80}\)
Tính bằng cách thuận tiện nhất :
\(\dfrac{3}{4}\)+\(\dfrac{2}{5}\)+\(\dfrac{3}{12}\)
`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`
Bài 6 : Tính bằng cách thuận tiện nhất
a) \(\dfrac{7}{6}x\)\(\dfrac{3}{4}+\dfrac{3}{4}x\)\(\dfrac{5}{6}-\dfrac{3}{4}\)
b) \(\dfrac{6x7x15x8}{4x21x10x3}\)
\(\dfrac{7}{6}\times\dfrac{3}{4}+\dfrac{3}{4}\times\dfrac{5}{6}-\dfrac{3}{4}\\ =\left(\dfrac{7}{6}+\dfrac{5}{6}-1\right)\times\dfrac{3}{4}\\ =1\times\dfrac{3}{4}=\dfrac{3}{4}\\ \dfrac{6\times7\times15\times8}{4\times21\times10\times3}\\ =\dfrac{2\times3\times7\times5\times3\times4\times2}{4\times7\times3\times5\times2\times3}\\ =2\)
1. Tính bằng cách thuận tiện nhất:
\(\dfrac{2}{5}x\dfrac{12}{3}+\dfrac{2}{5}x\dfrac{15}{3}+\dfrac{2}{5}\)
2. Tìm số tự nhiên a, biết: \(\dfrac{3}{4}< a< \dfrac{11}{4}\)
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
tính bằng cách thuận tiện nhất a, \(\dfrac{2}{9}\)+\(\dfrac{1}{6}\)+\(\dfrac{3}{5}\) b, \(\dfrac{9}{13}\)+\(\dfrac{4}{13}\)+\(\dfrac{2}{3}\)
a: =20/90+15/90+54/90=89/90
b: =(9/13+4/13)+2/3=1+2/3=5/3
Tính bằng cách thuận tiện nhất
\(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{4}{7}+\dfrac{5}{7}+\dfrac{6}{7}\)
\(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{4}{7}+\dfrac{5}{7}+\dfrac{6}{7}\)
\(=\dfrac{1+2+3+4+5+6}{7}=3\)
\(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{4}{7}+\dfrac{5}{7}+\dfrac{6}{7}\)
\(=\left(\dfrac{1}{7}+\dfrac{6}{7}\right)+\left(\dfrac{2}{7}+\dfrac{5}{7}\right)+\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\)
\(=1+1+1\)
\(=3\)