Tính bằng cách thuận tiện nhất :
a)\(\dfrac{81x49}{7x8}\)
b)\(\dfrac{105x69}{3x35}\)
c)\(\dfrac{77x39}{13x11}\)
Tính bằng cách thuận tiện nhất :
a) \(\frac{105x69}{3x35}\)
b) \(\frac{77x39}{13x11}\)
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 a, \(\dfrac{5}{13}\)x\(\dfrac{4}{15}\)x13= b, (\(\dfrac{3}{7}\)+\(\dfrac{5}{2}\))x\(\dfrac{7}{5}\)= c, \(\dfrac{1}{5}\)x\(\dfrac{11}{18}\)+\(\dfrac{11}{18}\)x\(\dfrac{3}{5}\)=
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{5\times4\times13}{13\times5\times3}=\dfrac{4}{3}\\ b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\dfrac{3}{7}\times\dfrac{7}{5}+\dfrac{5}{2}\times\dfrac{7}{5}=\dfrac{3}{5}+\dfrac{7}{2}=\dfrac{6}{10}+\dfrac{35}{10}=\dfrac{41}{10}\\ c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
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) \(\dfrac{6x7x15x8}{4x21x10x3}\)
\(\dfrac{7}{6}\times\dfrac{3}{4}+\dfrac{3}{4}\times\dfrac{5}{6}-\dfrac{3}{4}\\ =\left(\dfrac{7}{6}+\dfrac{5}{6}-1\right)\times\dfrac{3}{4}\\ =1\times\dfrac{3}{4}=\dfrac{3}{4}\\ \dfrac{6\times7\times15\times8}{4\times21\times10\times3}\\ =\dfrac{2\times3\times7\times5\times3\times4\times2}{4\times7\times3\times5\times2\times3}\\ =2\)
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`
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:
\(\dfrac{1}{2x3}\) + \(\dfrac{1}{3x4}\) + \(\dfrac{1}{4x5}\) + \(\dfrac{1}{5x6}\)
\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}\)
\(=\dfrac{1}{2}-\dfrac{1}{6}\)
\(=\dfrac{1}{3}\)
\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}=\dfrac{1}{2}-\dfrac{1}{6}=\dfrac{1}{3}\)
`1/(2*3)+1/(3*4)+1/(4*5)+...+1/(9*10)`
`=1/2-1/3+1/3-1/4+1/4-1/5+...+1/9-1/10`
`=1/2-1/10`
`=5/10-1/10`
`=4/10=2/5`
a) \(\dfrac{3}{7}\)+\(\dfrac{4}{9}\)+\(\dfrac{8}{14}\)+\(\dfrac{10}{18}\)
b) \(\dfrac{1}{2}\)x\(\dfrac{2}{3}\):\(\dfrac{5}{6}\)x\(\dfrac{5}{6}\)
bài này là bài tính bằng cách thuận tiện nhất nha !