Đáp án:

 $29)
a) \dfrac{9}{20}m^2\\
b)\dfrac{3}{100}m^2\\
c)\dfrac{23}{400}m^2\\
36)
a) \dfrac{2}{5}\\
b)\dfrac{2}{3}\\
41)
a) MCNN là 35\\
b) MCNN(5;25;3)=5^2.3=75\\
c)  MCNN(12;8;3;24)=2^3.3=24\\
42)
\dfrac{-12}{36};
\dfrac{24}{36};
\dfrac{18}{36};
\dfrac{-9}{36};
\dfrac{-27}{36};
\dfrac{6}{36};
\dfrac{-30}{36};
44)
 \dfrac{2}{7}<\dfrac{11}{13}\\$

Giải thích các bước giải:

 $29)
a) 45dm^2=0,45m^2=\dfrac{45}{100}m^2=\dfrac{9}{20}m^2\\
b)300cm^2=0,03m^2=\dfrac{3}{100}m^2\\
c) 57500mm^2=0,0575m^2=\dfrac{575}{10000}=\dfrac{23}{400}m^2\\
36)
a) \dfrac{4116-14}{10290-35}=\dfrac{4102}{10255}=\dfrac{4102:2006}{10255:2006}=\dfrac{2}{5}\\
b) \dfrac{2929-101}{2.1919+404}=\dfrac{2828}{4242}=\dfrac{2828:1414}{4242:1414}=\dfrac{2}{3}\\
41)
a) \dfrac{1}{5};\dfrac{-2}{7}$
MCNN là 35
b)$\dfrac{2}{5};\dfrac{3}{25};\dfrac{-1}{3}\\
5=5\\
25=5^2\\
3=3\\
\Rightarrow MCNN(5;25;3)=5^2.3=75\\
c) \dfrac{5}{12};\dfrac{-3}{8};\dfrac{-2}{3};\dfrac{7}{24}\\
12=2^2.3\\
8=2^3\\
3=3\\
24=2^3.3\\
\Rightarrow MCNN(12;8;3;24)=2^3.3=24\\
42)
\dfrac{-1}{3}=\dfrac{(-1).12}{3.12}=\dfrac{-12}{36}\\
\dfrac{2}{3}=\dfrac{2.12}{3.12}=\dfrac{24}{36}\\
\dfrac{-1}{-2}=\dfrac{1}{2}=\dfrac{18}{2.18}=\dfrac{18}{36}\\
\dfrac{6}{-24}=\dfrac{-1}{4}=\dfrac{(-1).9}{4.9}=\dfrac{-9}{36}\\
\dfrac{-3}{4}=\dfrac{(-3).9}{4.9}=\dfrac{-27}{36}\\
\dfrac{10}{60}=\dfrac{1}{6}=\dfrac{6}{6.6}=\dfrac{6}{36}\\
\dfrac{-5}{6}=\dfrac{(-5).6}{6.6}=\dfrac{-30}{36}\\
44)
\dfrac{3.4+3.7}{6.5+9}=\dfrac{3(4+7)}{3(10+3)}=\dfrac{11}{13}\\
\dfrac{6.9-2.17}{63.3-119}=\dfrac{54-34}{189-119}=\dfrac{20}{70}=\dfrac{2}{7}\\
\Rightarrow \dfrac{11}{13}=\dfrac{11.7}{13.7}=\dfrac{77}{91}\\
\dfrac{2}{7}=\dfrac{2.13}{7.13}=\dfrac{26}{91}\\
Vì 26<77\Rightarrow \dfrac{26}{91}<\dfrac{77}{91}\\
\Rightarrow \dfrac{2}{7}<\dfrac{11}{13}\\$

Đáp án:

Giải thích các bước giải:

29.

a)$45dm^{2}$ =$0,45m^{2}$ 

b)$300cm^{2}$ =$0,03m^{2}$ 

c)$57500mm^{2}$ =$0,0575m^{2}$ 

36.

a)$\frac{4116-14}{10290-35}$ =$\frac{4102}{10255}$ =$\frac{2}{5}$ 

b)$\frac{2929-101}{2.1919+404}$ =$\frac{2828}{4242}$ =$\frac{2}{3}$ 

41.

a)$\frac{1}{5}$ va $\frac{-2}{7}$ =$\frac{7}{35}$ va $\frac{-10}{35}$ 

⇒MCNN=35

b)$\frac{2}{5}$ ;$\frac{3}{25}$ ;$\frac{-1}{3}$ 

=$\frac{150}{375}$ ;$\frac{45}{375}$ ;$\frac{-125}{375}$ 

⇒MCNN=375

c)$\frac{5}{12}$ ;$\frac{-3}{8}$ ;$\frac{-2}{3}$ ;$\frac{7}{24}$ 

=$\frac{2880}{6912}$ ;$\frac{-2592}{6912}$ ;$\frac{-4608}{6912}$ ;$\frac{2016}{6912}$ 

⇒MCNN=6912

42.

$\frac{-1}{3}$=$\frac{-12}{36}$ 

$\frac{2}{3}$=$\frac{24}{36}$ 

$\frac{-1}{-2}$=$\frac{18}{36}$ 

$\frac{6}{-24}$=$\frac{-1}{4}$ =$\frac{-9}{36}$ 

$\frac{-3}{4}$=$\frac{-27}{36}$ 

$\frac{10}{60}$=$\frac{1}{6}$ =$\frac{6}{36}$ 

$\frac{-5}{6}$=$\frac{-30}{36}$ 

44.

$\frac{3.4+3.7}{6.5+9}$ va $\frac{6.9-2.17}{633-119}$ 

=$\frac{33}{39}$ va $\frac{20}{514}$

=$\frac{11}{13}$ va $\frac{10}{257}$ 

=$\frac{11.257}{13.257}$ va $\frac{10.13}{13.257}$ 

=$\frac{2827}{3341}$ va $\frac{130}{3341}$