dài vậy?Ghi đáp án thôi nhé!

a) 6,5% của 320m là 20,8 m

b) \(\dfrac{2}{7}\)của 21km là 6 km

c) 1,25 của 84 tấn là 105 tấn

d) \(1\dfrac{3}{4}\) của 1,25 giờ là 2,1875 giờ

e) \(1\dfrac{1}{4}\) của 2 giờ là 2,5 giờ

g) \(\dfrac{2}{11}\) của 22% là 4%

a) 6,5% của 320m=20,8m

b) \(\dfrac{2}{7}\) của 21km là 6km

c) 1,25 của 84 tấn là 105 tấn

d) \(1\dfrac{3}{4}\) của 1,25 giờ là 131,25 phút

e) \(1\dfrac{1}{4}\) của 2 giờ là 2,5 giờ

g) \(\dfrac{2}{11}\) của 22% là 0,04

\(\left|-1,25:\dfrac{7}{4}\right|+\left|-\dfrac{2}{7}\right|=\left|-\dfrac{5}{4}.\dfrac{4}{7}\right|+\dfrac{2}{7}\)

\(=\dfrac{5}{7}+\dfrac{2}{7}=1\)

\(\left|-1.25:\dfrac{7}{4}\right|+\left|\dfrac{-2}{7}\right|\)

\(=\left|\dfrac{-5}{4}\cdot\dfrac{4}{7}\right|+\left|\dfrac{-2}{7}\right|\)

\(=\dfrac{5}{7}+\dfrac{2}{7}=1\)

Giải:

a) \(25\%-\dfrac{5}{4}+\dfrac{11}{6}\)

\(=\dfrac{1}{4}-\dfrac{5}{4}+\dfrac{11}{6}\)

\(=-1+\dfrac{11}{6}\)

\(=\dfrac{5}{6}\)

Vậy ...

b) \(75\%:\dfrac{11}{5}-\left(0,5\right)^2.\left(-7\right)+2,5\left(\dfrac{23}{3}-\dfrac{17}{3}\right)\)

\(=\dfrac{3}{4}:\dfrac{11}{5}-\dfrac{1}{4}.\left(-7\right)+2,5.2\)

\(=\dfrac{15}{44} +\dfrac{7}{4}+5\)

\(=\dfrac{23}{11}+5\)

\(=\dfrac{78}{11}\)

Vậy ...

c) \(45:\dfrac{18}{7}+50\%-1,25\)

\(=45:\dfrac{18}{7}+\dfrac{1}{2}-\dfrac{5}{4}\)

\(=\dfrac{35}{2}+\dfrac{1}{2}-\dfrac{5}{4}\)

\(=18-\dfrac{5}{4}\)

\(=\dfrac{67}{4}\)

Vậy ...

\(a,\dfrac{1}{6}+\dfrac{7}{3}-\dfrac{1}{2}\\ =\dfrac{1}{6}+\dfrac{14}{6}-\dfrac{3}{6}\\ =\dfrac{12}{6}\\ =2\\ b,\left(-1\dfrac{5}{8}\right)+1,25:\left(1-\dfrac{9}{4}\right)\\ =\dfrac{-13}{8}+\dfrac{5}{4}:\dfrac{5}{4}\\ =\dfrac{-13}{8}+1\\ =\dfrac{-13}{8}+\dfrac{8}{8}\\ =\dfrac{5}{8}\)

A) \(\dfrac{1}{6}+\dfrac{7}{3}-\dfrac{1}{2}\)

Quy đồng: 

\(\dfrac{7}{3}=\dfrac{14}{6}\)

\(\dfrac{1}{2}=\dfrac{3}{6}\)

\(\dfrac{1}{6}=\dfrac{1}{6}\)

\(\dfrac{1}{6}+\dfrac{14}{6}-\dfrac{3}{6}=\dfrac{12}{6}\)

Rút gọn: \(\dfrac{12}{6}=\dfrac{12\div6}{6\div6}=2\)

Bài 4: 

a) \(\dfrac{4}{3}+\left(1,25-x\right)=2,25\)

\(1,25-x=2,25-\dfrac{4}{3}=\dfrac{9}{4}-\dfrac{4}{3}\)

\(1,25-x=\dfrac{11}{12}\)

\(x=1,25-\dfrac{11}{12}=\dfrac{5}{4}-\dfrac{11}{12}\)

\(x=\dfrac{1}{3}\)

b) \(\dfrac{17}{6}-\left(x-\dfrac{7}{6}\right)=\dfrac{7}{4}\)

\(x-\dfrac{7}{6}=\dfrac{17}{6}-\dfrac{7}{4}=\dfrac{34}{12}-\dfrac{21}{12}\)

\(x-\dfrac{7}{6}=\dfrac{13}{12}\)

\(x=\dfrac{13}{12}+\dfrac{7}{6}=\dfrac{13}{12}+\dfrac{14}{12}\)

\(x=\dfrac{27}{12}=\dfrac{9}{4}\)

c) \(4-\left(2x+1\right)=3-\dfrac{1}{3}=\dfrac{9}{3}-\dfrac{1}{3}\)

\(4-\left(2x+1\right)=\dfrac{8}{3}\)

\(2x+1=\dfrac{8}{3}+4=\dfrac{8}{3}+\dfrac{12}{3}\)

\(2x+1=\dfrac{20}{3}\)

\(2x=\dfrac{20}{3}-1=\dfrac{20}{3}-\dfrac{3}{3}\)

\(2x=\dfrac{17}{3}\)

\(x=\dfrac{17}{3}.\dfrac{1}{2}=\dfrac{17}{6}\)

Bài 15:

a) \(\left(\dfrac{-2}{3}\right)^9:x=\dfrac{-2}{3}\)

\(x=\left(\dfrac{-2}{3}\right)^9:\dfrac{-2}{3}=\left(\dfrac{-2}{3}\right)^{9-1}\)

\(=>x=\left(\dfrac{-2}{3}\right)^8\)

b) \(x:\left(\dfrac{4}{9}\right)^5=\left(\dfrac{4}{9}\right)^4\)

\(x=\left(\dfrac{4}{9}\right)^4.\left(\dfrac{4}{9}\right)^5=\left(\dfrac{4}{9}\right)^{4+5}\)

\(=>x=\left(\dfrac{4}{9}\right)^9\)

c) \(\left(x+4\right)^3=-125\)

\(\left(x+4\right)^3=\left(-5\right)^3\)

\(=>x+4=-5\)

\(x=-5-4\)

\(=>x=-9\)

d) \(\left(10-5x\right)^3=64\)

\(\left(10-5x\right)^3=4^3\)

\(=>10-5x=4\)

\(5x=10-4\)

\(5x=6\)

\(=>x=\dfrac{6}{5}\)

e) \(\left(4x+5\right)^2=81\)

\(\Leftrightarrow\left[{}\begin{matrix}\left(4x+5\right)^2=\left(-9\right)^2\\\left(4x+5\right)^2=9^2\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}4x+5=-9\\4x+5=9\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}4x=-14\\4x=4\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-14}{4}\\x=1\end{matrix}\right.\)

Bài 16:

a) \(4-1\dfrac{2}{5}-\dfrac{8}{3}\)

\(=4-\dfrac{7}{5}-\dfrac{8}{3}\)

\(=\dfrac{60-21-40}{15}=\dfrac{-1}{15}\)

b) \(-0,6-\dfrac{-4}{9}-\dfrac{16}{15}\)

\(=\dfrac{-3}{5}+\dfrac{4}{9}-\dfrac{16}{15}\)

\(=\dfrac{\left(-27\right)+20-48}{45}=\dfrac{-55}{45}=\dfrac{-11}{9}\)

c) \(-\dfrac{15}{4}.\left(\dfrac{-7}{15}\right).\left(-2\dfrac{2}{5}\right)\)

\(=\dfrac{7}{4}.\dfrac{-12}{5}\)

\(=\dfrac{-21}{5}\)

\(#Wendy.Dang\)

Uh, chừa sau k dám học muộn nx

Đăng từng bài `1` thôi cậu ơii

a: =3/4-5/4+3/2x12/5=-1/2+36/10=-5/10+36/10=31/10

b: \(=\dfrac{-7}{13}\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\dfrac{7}{13}+8=8\)