Thực hiện phép tính (tính hợp lí nếu có thể):
(-1,6) . \(\dfrac{-15}{64}\) + ( 0,8 - 2\(\dfrac{4}{15}\) ) : 3\(\dfrac{2}{3}\)
Thực hiện phép tính hợp lí (nếu có thể):
A = \(\dfrac{11}{9}.\dfrac{-3}{2}-\dfrac{11}{9}.\dfrac{15}{2}+\left(-2021\right)^0\)
A= \(\dfrac{11}{9}\).\(\dfrac{-3}{2}\)- \(\dfrac{11}{9}\).\(\dfrac{15}{2}\)+(2021)0
= \(\dfrac{11}{9}\)(\(\dfrac{-3}{2}\)-\(\dfrac{15}{2}\)) + 1
= \(\dfrac{11}{9}\)(-9) + 1
= -11 + 1
= -10
Thực hiện phép tính (tính nhanh nếu có thể)
\(\dfrac{11}{15}.\dfrac{4}{11}+\dfrac{11}{15}.\dfrac{5}{11}+\dfrac{11}{15}.\dfrac{2}{11}\)
= \(\dfrac{11}{15}\). \(\left(\dfrac{4}{11}+\dfrac{5}{11}+\dfrac{2}{11}\right)\)
= \(\dfrac{11}{15}\). 1
=\(\dfrac{11}{15}\)
\(=\dfrac{11}{15}\cdot\left(\dfrac{4}{11}+\dfrac{5}{11}+\dfrac{2}{11}\right)=\dfrac{11}{15}\cdot\dfrac{11}{11}=\dfrac{11}{15}\)
11/15 . ( 4/11 +5/11 + 2/11 )
= 11/15 . 1
= 11/15
Bài 1: Thực hiện phép tính: (tính nhanh nếu có thể)
f) \(\dfrac{4}{15}.\dfrac{1}{3}.\dfrac{15}{20}\)
`4 / 15 . 1 / 3 . 15 / 20`
`= [ 4 . 1 . 15 ] / [ 15 . 3 . 20 ]`
`= [ 4 . 1 . 15 ] / [ 15 . 3 . 4 . 5 ]`
`= 1 / [ 3 . 5 ]`
`= 1 / 15`
\(=\left(\dfrac{4}{15}.\dfrac{15}{20}\right).\dfrac{1}{3}=\dfrac{60}{300}.\dfrac{1}{3}=\dfrac{60}{900}=\dfrac{1}{15}\)
\(=\dfrac{4.1.15}{15.3.5.4}=\dfrac{1}{3.5}=\dfrac{1}{15}\)
Thực hiện phép tính( hợp lí nếu có thể)
\(\dfrac{-3}{5}:\dfrac{7}{5}-\dfrac{3}{5}:\dfrac{7}{5}+2\dfrac{3}{5}\)
\(=\dfrac{-3}{5}:\dfrac{7}{5}-\dfrac{3}{5}:\dfrac{7}{5}+2\dfrac{3}{5}\)
\(=-\dfrac{6}{5}\times\dfrac{5}{7}+\dfrac{13}{5}=\dfrac{61}{35}\)
=\(\dfrac{-3}{5}\).\(\dfrac{5}{7}\)-\(\dfrac{3}{5}\).\(\dfrac{5}{7}\)+\(\dfrac{13}{5}\)
=(\(\dfrac{-3}{5}\)-\(\dfrac{3}{5}\)+\(\dfrac{13}{5}\)).\(\dfrac{5}{7}\)
=\(\dfrac{13}{5}\).\(\dfrac{5}{7}\)
=\(\dfrac{13}{1}\).\(\dfrac{1}{7}\)
=\(\dfrac{13}{7}\)
\(\text{Thực hiện phép tính một cách hợp lí:}\)
\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}:\dfrac{1}{5}+\dfrac{3}{5}.\dfrac{1}{3}\) \(\left(4-\dfrac{5}{12}\right):2+\dfrac{5}{24}\)
\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}:\dfrac{1}{5}+\dfrac{3}{5}.\dfrac{1}{3}\)
=\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}.\dfrac{5}{1}+\dfrac{3}{5}.\dfrac{1}{3}\)
=\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{3}+\dfrac{3}{5}.\dfrac{1}{3}\)
=\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{1}{3}.2+\dfrac{3}{5}.\dfrac{1}{3}\)
=\(\dfrac{1}{3}.\left(\dfrac{2}{5}+\dfrac{3}{5}-2\right)\)=\(\dfrac{1}{3}.\left(-1\right)=\dfrac{-1}{3}\)
\(\left(4-\dfrac{5}{12}\right):2+\dfrac{5}{24}\)
=\(\left(4-\dfrac{5}{12}\right).\dfrac{1}{2}+\dfrac{5}{24}\)
=\(4.\dfrac{1}{2}-\dfrac{5}{12}.\dfrac{1}{2}+\dfrac{5}{24}\)
=\(2-\dfrac{5}{24}+\dfrac{5}{24}=2\)
Giải:
\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}:\dfrac{1}{5}+\dfrac{3}{5}.\dfrac{1}{3}\)
\(=\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{3}+\dfrac{3}{5}.\dfrac{1}{3}\)
\(=\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{1}{3}.2+\dfrac{3}{5}.\dfrac{1}{3}\)
\(=\dfrac{1}{3}.\left(\dfrac{2}{5}-2+\dfrac{3}{5}\right)\)
\(=\dfrac{1}{3}.\left(-1\right)\)
\(=\dfrac{-1}{3}\)
\(\left(4-\dfrac{5}{12}\right):2+\dfrac{5}{24}\)
\(=\dfrac{43}{12}:2+\dfrac{5}{24}\)
\(=\dfrac{43}{24}+\dfrac{5}{24}\)
\(=2\)
Thực hiện phép tính (hợp lí nếu có thể):
a) (\(\dfrac{-6}{11}\)) . \(\dfrac{7}{10}\) . \(\dfrac{11}{-6}\) . (-20)
b) (\(-1\dfrac{1}{2}\)) : \(\dfrac{3}{4}\) . \(-4\dfrac{1}{2}\))
c) \(13\dfrac{2}{7}\) : (\(\dfrac{-8}{9}\)) + \(2\dfrac{5}{7}\) : (\(\dfrac{-8}{9}\))
\(a.\left[-\dfrac{6}{11}.\dfrac{11}{-6}\right].\dfrac{7}{10}.\left(-20\right)=1.7.\left(-2\right)=-14\)
\(b.\dfrac{-1}{2}:\dfrac{3}{4}.\dfrac{-7}{2}=\dfrac{7}{4}:\dfrac{3}{4}=\dfrac{7}{3}\)
\(c.\dfrac{93}{7}:-\dfrac{8}{9}+\dfrac{19}{7}:\dfrac{-8}{9}=\left(\dfrac{93}{7}+\dfrac{19}{7}\right):-\dfrac{8}{9}=\dfrac{-9}{8}.\dfrac{112}{7}=-18\)
Thực hiện phép tính (hợp lí nếu có thể):
a) \(13\dfrac{2}{7}\) : (\(\dfrac{-8}{9}\)) + \(2\dfrac{5}{7}\) : (\(\dfrac{-8}{9}\))
b) (\(\dfrac{-6}{11}\)) . \(\dfrac{7}{10}\) . (\(\dfrac{11}{-6}\)) . (-20)
c) (\(-1\dfrac{1}{2}\)) : \(\dfrac{3}{4}\) . (\(-4\dfrac{1}{2}\))
a) \(=\left(13\dfrac{2}{7}+2\dfrac{5}{7}\right):\left(-\dfrac{8}{9}\right)\)
\(=16:\dfrac{-8}{9}=\dfrac{-8\cdot\left(-2\right)\cdot9}{-8}=-18\)
b)
\(=\left(\dfrac{-6}{11}\cdot\dfrac{11}{-6}\right)\cdot\dfrac{7\cdot10\cdot\left(-2\right)}{10}\)
\(=-14\)
c) \(=\dfrac{-1}{2}\cdot\dfrac{4}{3}\cdot\dfrac{-7}{2}\)
\(=\dfrac{-1\cdot2\cdot2\cdot\left(-7\right)}{2\cdot3\cdot2}=\dfrac{7}{3}\)
Thực hiện phép tính ( tính nhanh nếu có thể ) :
a) \(\dfrac{3}{5}+\dfrac{1}{5}.\dfrac{-17}{9}\)
b) \(\left(-\dfrac{4}{15}-\dfrac{18}{19}\right)-\left(\dfrac{20}{19}+\dfrac{11}{15}\right)\)
\(a,\dfrac{3}{5}+\dfrac{1}{5}.\dfrac{-17}{9}=\dfrac{3}{5}-\dfrac{17}{45}=\dfrac{27}{45}-\dfrac{17}{45}=\dfrac{10}{45}=\dfrac{2}{9}\\ b,\left(-\dfrac{4}{15}-\dfrac{18}{19}\right)-\left(\dfrac{20}{19}+\dfrac{11}{15}\right)=-\dfrac{4}{15}-\dfrac{18}{19}-\dfrac{20}{19}-\dfrac{11}{15}=\left(-\dfrac{4}{15}-\dfrac{11}{15}\right)-\left(\dfrac{18}{19}+\dfrac{20}{19}\right)=-1-2=-3\)
\(a,=\dfrac{3}{5}+\left(-\dfrac{17}{45}\right)=\dfrac{2}{9}\)
\(b,=-\dfrac{4}{15}-\dfrac{18}{19}-\dfrac{20}{19}-\dfrac{11}{15}=-3\)
a. 3/5+1/5.-17/9
=3/5+-17/45
=27/45+-17/45
=2/9
b. (-4/15-18/19)-(20/19+11/15)
=-4/15-18/19-20/19-11/15
=(-4/15-11/15)-(18/19-20/19)
=(-1)-(-2/19)
=(-19/19)-(-2/19)
=-17/19
Thực hiện phép tính (tính nhanh nếu có thể):
a/ \(\dfrac{3}{5}+\dfrac{1}{5}.\dfrac{-17}{9}\) b/ \(\left(-\dfrac{4}{15}-\dfrac{18}{19}\right)\)-\(\left(\dfrac{20}{19}+\dfrac{11}{15}\right)\)
Thực hiện phép tính (tính nhanh nếu có thể)
a) \(\dfrac{1}{2}\) + \(\dfrac{-2}{3}\)
b) \(\dfrac{-7}{3}\) . \(\dfrac{15}{9}\) - \(\dfrac{10}{9}\)
c) [(-0,7) : 0,07 + 9] . ( 1,3 . 2,5 + 1,3 . 7,5 )
a)\(=\dfrac{3}{6}-\dfrac{4}{6}=-\dfrac{1}{6}\)
b)\(=-\dfrac{35}{9}-\dfrac{10}{9}=-\dfrac{45}{9}=-5\)
c)\(=\left[-10+9\right].\left[1,3.\left(2,5+7,5\right)\right]=-1.\left[1,3.10\right]=-1.13=-13\)