A= 37.2+14.01+5.99+2.8=37.2+2.8+14.01+5.99=60

B=6.43+12.56+7.44+3.15+6.85+1.23+2.34=40

A+B=60+40=100

Thì cứ thêm sô 0 vào sau sấu sau dấy phầy là được mà @@ . Giá trị không đổi đó 

0,3 = 0,300

0,4=0,400

0,02=0,020

0,03=0,030

0,04=0,040

0,12=0,120

0,23=0,230

0,34=0,340

1,2=1,200

1,23=1,230

2,34=2,340

6,43+12,46+6,97+7,54+3,25+6,75+3,03+1,23+2,34

=(6,43+2,34+1,23)+(12,46+7,54)+(6,97+3,03)+(3,25+6,75)=10+20+10+10=10*3+20=30+20=50

Hiệu cũ là

20,06-3,45+1,23=18,84

Đáp số : 18,84

2,34(56)=2+1711/4950=11611/4950

13,25(3)=13+19/75=994/75

56,2(5)=56+23/90=5063/90

43,2(34)=43+116/495=21401/495

\(2,34\left(56\right)=2,34+\frac{1}{100}.56.\frac{1}{99}=\frac{11611}{4950}\)

\(13,25\left(3\right)=13,25+\frac{1}{100}.3.\frac{1}{9}=\frac{994}{75}\)

\(56,2\left(5\right)=56,2+\frac{1}{10}.5.\frac{1}{9}=\frac{5063}{90}\)

\(43,2\left(34\right)=43,2+\frac{1}{10}.34.\frac{1}{99}=\frac{21401}{495}\)

a: \(\dfrac{5}{3}\cdot\dfrac{7}{10}=\dfrac{5}{10}\cdot\dfrac{7}{3}=\dfrac{14}{3}>2\)

\(\dfrac{5}{7}:\dfrac{7}{10}=\dfrac{5}{7}\cdot\dfrac{10}{7}=\dfrac{50}{49}< 2\)

=>\(\dfrac{5}{3}\cdot\dfrac{7}{10}>\dfrac{5}{7}:\dfrac{7}{10}\)

b: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

\(\dfrac{8}{9}:\dfrac{4}{3}=\dfrac{8}{9}\cdot\dfrac{3}{4}=\dfrac{8}{4}\cdot\dfrac{3}{9}=\dfrac{2}{3}\)

Do đó: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{8}{9}:\dfrac{4}{3}\)

c: \(\dfrac{5}{11}\cdot\dfrac{33}{15}=\dfrac{5}{15}\cdot\dfrac{33}{11}=\dfrac{3}{3}=1\)

\(\dfrac{6}{17}\cdot\dfrac{34}{25}=\dfrac{34}{17}\cdot\dfrac{6}{25}=2\cdot\dfrac{6}{25}=\dfrac{12}{25}< 1\)

=>\(\dfrac{5}{11}\cdot\dfrac{33}{15}>\dfrac{6}{17}\cdot\dfrac{34}{25}\)

d: \(\dfrac{15}{19}\cdot\dfrac{38}{5}=\dfrac{15}{5}\cdot\dfrac{38}{19}=3\cdot2=6\)

\(\dfrac{15}{16}:\dfrac{3}{8}=\dfrac{15}{16}\cdot\dfrac{8}{3}=\dfrac{15}{3}\cdot\dfrac{8}{16}=\dfrac{5}{2}\)<6

=>\(\dfrac{15}{19}\cdot\dfrac{38}{5}>\dfrac{15}{16}:\dfrac{3}{8}\)

Số thập phân vô hạn tuần hoàn à