nhầm em nhé

\(\dfrac{13}{3}:\left(0,25+1,25\right)-\dfrac{20}{3}=\dfrac{13}{3}:\left(\dfrac{1}{4}+\dfrac{5}{4}\right)-\dfrac{20}{3}=\dfrac{13}{3}:\dfrac{3}{2}-\dfrac{20}{3}=\dfrac{13}{3}.\dfrac{2}{3}-\dfrac{20}{3}=\dfrac{26}{9}-\dfrac{20}{3}=\dfrac{26}{9}-\dfrac{60}{9}=\dfrac{-34}{9} \)

\(4\dfrac{1}{3}:\left(25\%+1,25\right)-6\dfrac{2}{3}=\dfrac{13}{3}+\left(\dfrac{1}{4}+\dfrac{5}{4}\right)-\dfrac{20}{3}=\dfrac{13}{3}+\dfrac{3}{2}-\dfrac{20}{3}=\left(\dfrac{13}{3}-\dfrac{20}{3}\right)+\dfrac{3}{2}=\dfrac{-7}{3}+\dfrac{3}{2}=\dfrac{-14}{6}+\dfrac{9}{6}=\dfrac{-5}{6}\)

a) \(57,65\) m \(=576,5\) dm

b) \(1\) m³ \(45\) dm³ \(< 1,45\) m³

c)  \(5\) tấn \(25\) kg \(=5,025\) tấn

d) 2 giờ 40 phút > 2,4 giờ

C

B

d) \(x+\dfrac{3}{4}=\dfrac{36}{144}.\dfrac{-12}{9}\)

\(\Rightarrow x+\dfrac{3}{4}=\dfrac{-1}{3}\)

\(\Rightarrow x=\dfrac{-1}{3}-\dfrac{3}{4}\)

\(\Rightarrow x=\dfrac{-4}{12}-\dfrac{9}{12}\)

\(\Rightarrow x=\dfrac{-13}{12}\)

e)

\(\dfrac{8}{23}.\dfrac{46}{24}=\dfrac{1}{3}.x\)

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

\(\Rightarrow x=\dfrac{2}{3}:\dfrac{1}{3}\)

\(\Rightarrow x=\dfrac{2}{3}.3\)

\(\Rightarrow x=2\)

f)

\(\dfrac{1}{5}:x=\dfrac{1}{5}-\dfrac{1}{7}\)

\(\dfrac{1}{5}:x=\dfrac{7}{35}-\dfrac{5}{35}\)

\(\dfrac{1}{5}:x=\dfrac{2}{35}\)

\(\Rightarrow x=\dfrac{1}{5}:\dfrac{2}{35}\)

\(\Rightarrow x=\dfrac{1}{5}.\dfrac{35}{2}\)

\(\Rightarrow x=\dfrac{7}{2}\)

a) \(\dfrac{4}{7}+\dfrac{3}{4}+\dfrac{2}{7}+\dfrac{5}{4}+\dfrac{1}{7}=\left(\dfrac{4}{7}+\dfrac{2}{7}+\dfrac{1}{7}\right)+\left(\dfrac{3}{4}+\dfrac{5}{4}\right)=1+2=3\)

b) \(-\dfrac{5}{7}+\dfrac{3}{4}+-\dfrac{1}{5}+-\dfrac{2}{7}+\dfrac{1}{4}=\left[\left(-\dfrac{5}{7}\right)+\left(-\dfrac{2}{7}\right)\right]+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+-\dfrac{1}{5}=\left(-1\right)+1+\left(-\dfrac{1}{5}\right)=\left(-\dfrac{1}{5}\right)\) 

c) \(\dfrac{5}{13}+\dfrac{-5}{7}+-\dfrac{20}{41}+\dfrac{8}{13}+-\dfrac{21}{41}=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left[\left(-\dfrac{20}{41}\right)+\left(-\dfrac{21}{41}\right)\right]+\left(-\dfrac{5}{7}\right)=1+\left(-1\right)+\left(-\dfrac{5}{7}\right)=\left(-\dfrac{5}{7}\right)\)

d) \(\dfrac{1}{28}+\left(-\dfrac{1}{14}\right)+\dfrac{3}{28}+\left(-\dfrac{1}{7}\right)+\dfrac{3}{14}=\left(\dfrac{1}{28}+\dfrac{3}{28}\right)+\left[\left(-\dfrac{1}{14}\right)+\dfrac{3}{14}\right]+\left(-\dfrac{1}{7}\right)=\dfrac{1}{7}+\dfrac{1}{7}+\left(-\dfrac{1}{7}\right)=\dfrac{1}{7}\)

a) S

b) Đ

c) Đ

d) S

a) Vì AN+AM= MN

\(\Rightarrow AN=MN-AM=5-3=2\left(cm\right)\)

b) VÌ O là trung điểm nên

\(\Rightarrow OA=ON=\dfrac{AN}{2}=\dfrac{2}{2}=1\left(cm\right)\)

Vì MO= AM+AO

\(\Rightarrow MO=3+1=4\left(cm\right)\)