\(\frac{32.53-21}{53.31+32}=\frac{53.31+53.1-21}{53.31+32}=\frac{53.31+53-21}{53.31+32}=\frac{53.31+32}{53.31+32}=\frac{1}{1}=1\)

\(\frac{32.53-21}{53.31+32}=\frac{31.53+53-21}{53.31+32}=\frac{31.53+32}{53.31+32}=1\)

Câu 1 . A<B
Câu 2 .A<B

a)B = 32 x 53 - 31 =31 x 53 + 53 -31 = 31 x 53 + 22

mà 32 < 22

-> A >B

a,

ta có:

B=32*53-31

  =(31+1)*53-31

  =31*53+53-31

  =31*53+22

suy ra B<A

b,

Ta có:

C=2000*2000

  =(1990+10)*(2010-10)

  =1990*2010-1990*10+2010810-10*10

  =1990*2010+10*(2010-1990-10)

  =1990*2010+100

  suy ra C>D

    53 x 31+ 32

=  1643 + 32

=  1643 + 32 

=   1675

Vậy : 53 x 31+ 32 = 1675

\(53.31+32\)

\(=1643+32\)

\(=1675\)

Ta có:

\(A=53\times31+32\)

\(A=53\times\left(32-1\right)+32\)

\(A=53\times32-53+32\)

\(A=32\times54-53\)

\(A=1728-53\)

\(A=1675\)

Toán lớp 5

25.83-10>31.26+10

32.53-31<53.31+32

theo mình dấu chấm là dấu nhân đó nhé!

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{7}+...+\frac{1}{32}-\frac{1}{81}\)

\(=1-\frac{1}{81}\)

\(=\frac{80}{81}\)

18/21 +19/32 +3/21+13/32

= (18/21 + 3/21) + (19/32 + 13/32)

= 1 + 1=2

2

2

48/49

Đặt \(B=\frac{1}{1.2}+\frac{5}{2.7}+\frac{8}{7.15}+\frac{13}{15.28}+\frac{21}{28.49}+\frac{32}{49.81}\)

   \(\Rightarrow B=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}+\frac{1}{28}-\frac{1}{49}+\frac{1}{49}-\frac{1}{81}\)

   \(\Rightarrow B=1-\frac{1}{81}\)

      \(\Rightarrow B=\frac{80}{81}\)

\(\frac{75}{100}+\frac{18}{21}+\frac{19}{32}+\frac{1}{4}+\frac{3}{21}+\frac{13}{32}\)

\(=\left(\frac{75}{100}+\frac{1}{4}\right)+\left(\frac{18}{21}+\frac{3}{21}\right)+\left(\frac{19}{32}+\frac{13}{31}\right)\)

\(=1+1+1\)

\(=3\)